JTJN7     IJKW 


Wining:  dept. 


LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


Class 


HEAT  ENERGY  AND 
FUELS 


PYROMETRY,  COMBUSTION,  ANALYSIS  OF 
FUELS    AND    MANUFACTURE    OF 
CHARCOAL,    COKE    AND 
FUEL  GASES 


BY 

HANNS   v.  JUPTNER 

«/ 

PROFESSOR,    IMPERIAL   AND    ROYAL    TECHNICAL    INSTITUTE, 
VIENNA 


TRANSLATED    BY 

OSKAR   NAGEL,  Pn.D. 


"HE 

UNIVER 

iF 


NEW  YORK 
McGRAW   PUBLISHING   COMPANY 

239  WEST  39TH  STREET 
1908 


.      .'    B 


COPYRIGHT,  1908, 

BY    THE 

McGRAW   PUBLISHING   COMPANY 
NEW  YORK 


Stanbopc  ipress 

F.    H.  GILSON     COMPANY 
BOSTON.     U.S. A 


TRANSLATOR'S  PREFACE 


PROFESSOR  HANNS  VON  JUPTNER  has  divided  the  study  of 
chemical  engineering  into  two  groups,  namely:  energy  and 
matter ;  and  beginning  with  a  general  discussion  of  the  various 
forms  of  energy,  has  written  four  volumes  covering  the  subject 
both  theoretically  and  practically. 

The  present  volume  deals  with  heat  energy  and  fuels,  and 
contains  a  large  amount  of  carefully  tabulated  data  in  conven- 
ient form  for  use.  •  A  great  deal  of  this  data  is  new  and  will  be 
welcomed  by  chemists,  metallurgists  and  engineers. 

Although  the  book  is  intended  for  use  in  universities  and 
engineering  schools  it  is  of  equal  value  to  practising  engineers, 
since  it  gives  not  only  the  fundamental  principles,  but  also  the 
latest  experimental  data  and  practice. 

Among  the  topics  of  greatest  practical  interest  are  :  Measure- 
ment of  high  temperatures  and  late  data  on  the  melting  points 
of  various  substances ;  discussion  of  incomplete  combustion, 
combustion  temperatures  and  combustion  at  constant  volume 
and  constant  pressure,  and  an  immense  amount  of  data  on  solid, 
liquid  and  gaseous  fuels  and  their  production.  The  chapters 
on  the  gasification  of  fuels,  which  contain  the  results  of  the 
author's  own  experiments  as  well  as  those  of  Strache  and  Jahoda, 
are  of  especial  value. 

The  book  has  been  extremely  well  received  in  Europe,  where 
it  is  widely  used  both  in  schools  and  in  practice  as  a  text-book 
and  handbook. 

THE  TRANSLATOR. 

NEW  YORK,  November,  1908. 


iii 


181331 


CONTENTS 


INTRODUCTION. 

CHAPTER  PAGE 

I.   GENERAL  REMARKS 1 

II.   FORMS  OF  ENERGY 11 

VOLUME   I.     HEAT  ENERGY  AND   FUELS. 

Part  I.    Heat  Measurement,  Combustion  and  Fuels. 

I.   THE  MEASUREMENT  OF  HIGH  TEMPERATURES  (PYROMETRY)  . .  37 

II.    PYROMETRY  (Continued) 53 

III.  PYROMETRY   (Conclusion).     OPTICAL  METHODS  OF  MEASURING 

TEMPERATURES 68 

IV.  COMBUSTION  HEAT  AND  ITS  DETERMINATION 91 

V.   DIRECT  METHODS  FOR  DETERMINING  THE  COMBUSTION  HEAT  110 

VI.   INCOMPLETE  COMBUSTION 117 

VII.   COMBUSTION  TEMPERATURE 127 

VIII.   FUELS  (In  General) 141 

IX.   WOOD 145 

X.   FOSSIL  SOLID  FUELS  (In  General) 155 

XI.    PEAT 166 

XII.   BROWN  COAL  (Lignite) 173 

XIII.  BITUMINOUS  AND  ANTHRACITE  COALS 178 

XIV.  ARTIFICIAL  SOLID  FUELS 188 

XV.   CHARCOAL 191 

XVI.   PEAT-COAL,  COKE  AND  BRIQUETTES 214 

XVII.   COKING  APPARATUS 230 

XVIII.    LIQUID  FUELS  . 241 

XIX.   GASEOUS  FUELS 243 

XX.   PRODUCER  GAS 246 

XXI.   WATER  GAS 268 

XXII.   DOWSON  GAS,  BLAST  FURNACE  GAS  AND  REGENERATED  COM- 
BUSTION GASES 287 

XXIII.   APPARATUS  FOR  THE  PRODUCTION  OF  FUEL  GASES 292 

INDEX 303 


'OF  THE 
UNIVERSITY 

^N^LIFO* 


HEAT  ENEKGY   AND   FUELS 


INTRODUCTION. 

CHAPTER  I. 
GENERAL  REMARKS. 

IF  we  consider  the  immense  strides  that  technical  science 
has  made  in  the  second  half  of  the  nineteenth  century;  if  we 
observe  how  prosperity  is  increasing,  especially  in  the  countries 
prominent  in  engineering;  and  how,  as  a  natural  sequence,  the 
standing  and  influence  of  engineers  are  constantly  growing  in 
these  countries,  we  are  forced  to  ask  by  what  means  all  this  has 
come  to  pass  —  in  other  words,  to  what  circumstances  are  we 
indebted  for  this  remarkable  progress? 

A  close  study  of  the  development  of  technical  science  shows 
its  close  connection  with  the  natural  development  of  mankind. 

At  first,  man  had  no  other  resource  in  his  struggle  with  wild 
animals  and  natural  forces  than  himself,  that  is,  the  organs  given 
him  by  nature.  Necessity  taught  him  how  to  protect  himself 
from  cold  by  means  of  clothes,  to  seek  protection  from  expo- 
sure to  the  weather,  and  led  him  to  build  dwellings.  Nature 
gave  him  a  cave  for  his  first  home,  but  he  soon  learned  to 
construct  artificial  shelters. 

In  his  struggles  with  wild  animals  he  tried  to  increase  his 
efficiency.  For  this  purpose  he  first  tried  to  lengthen  his  reach 
with  a  stick.  Then  he  found  that  a  thrown  stone  was  able  to 
act  far  beyond  the  immediate  range  of  his  arm. 

He  soon  found  that  there  were  expedients  for  using  the 
strength  of  his  muscles  to  greater  advantage,  and  he  began  to 
devise  primitive  tools  in  the  widest  sense  of  the  word.  His 
problem  now  was  to  select  the  material  most  adapted  to  his 
purposes  from  the  mineral,  vegetable  and  animal  kingdoms; 
thus  his  knowledge  of  nature  was  considerably  increased.  As 

l 


2  HEAT  ENERGY  AND  FUELS 

the  material  suitable  for  his  tools  and  implements  could  not 
always  be  found  near  at  hand,  man  had  to  get  it  by  barter, 
and  we  have  the  beginning  of  commerce  and  traffic. 

It  was  a  great  advance  in  the  progress  of  civilization  when 
man  learned  to  use  fire;  this  discovery  is  of  special  inter- 
est to  us  as  chemical  industry  depends  on  it.  In  close 
connection  are  the  manufacture  of  burned  clay-vessels  (the 
beginning  of  ceramics)  and  the  production  of  metals,  both  of 
which  are  of  the  greatest  importance  in  the  development  of 
civilization,  as  they  furnish  materials  that  are  especially  suited 
for  the  manufacture  of  implements  and  arms  of  various  kinds. 
Herewith  are  connected  other  improvements,  such  as  the  prep- 
aration of  food  by  boiling,  broiling,  roasting  and  baking,  the 
preparation  of  alcoholic  beverages,  the  use  of  fermentation  in 
baking  bread,  dyeing,  tanning,  etc. 

At  first  man  lived  alone"  or  banded  in  small  families. 
With  increasing  civilization,  especially  after  the  beginning  of 
agriculture  and  cattle-breeding,  which  enabled  a  number  of 
people  to  live  together  by  insuring  the  necessities  of  life,  clans 
were  formed  by  the  union  of  families,  and  therefrom,  grad- 
ually, the  nations.  Thus  division  of  labor  was  made  possi- 
ble; the  individual  members  of  such  families  or  clans  were 
enabled  to  devote  their  time  to  the  solution  of  certain  tasks, 
according  to  their  individual  skill  and  inclination.  Gradual 
evolution  along  these  lines,  in  the  course  of  thousands  of  years, 
resulted  in  the  differentiation  of  skilled  labor  into  distinct  trades 
and  professions,  and  on  this  foundation  modern  engineering  and 
the  modern  industrial  system  developed. 

In  the  Middle  Ages  the  skilled  artisans  were  working  by  rule 
of  thumb,  and  frequently  kept  their  methods  of  working  secret. 
At  that  time  there  was  no  engineering  science  in  existence  in 
the  modern  sense  of  this  word.  This  is  but  natural,  since  the 
process  of  reasoning  was  hampered  by  insufficient  and  conflicting 
data;  and  was,  moreover,  entirely  different  from  our  modern 
way  of  thinking,  the  base  of  which  is  natural  science.  This 
interfered  with  the  progress  of  the  trades  and  the  development 
of  progressive  methods.  The  period  of  Renaissance  only  brought 
a  change  by  guiding  us  back  to  the  observation  of  nature. 

This  change,  naturally,  could  take  place  only  slowly  and 
gradually,  as  there  is  no  more  difficult  task  for  a  man,  not 


GENERAL  REMARKS  3 

accustomed  to  it  from  his  youth,  than  to  observe  and  think 
accurately;  on  the  other  hand,  the  scientists  formed  at  that  time 
an  entirely  separate  class,  just  as  did  the  trades  and  profes- 
sions, and  a  long  time  was  required  before  the  gap  between  the 
two  was  bridged  over,  so  that  science  and  the  trades  could  work 
together. 

At  first  the  sciences  had  to  be  developed,  before  being 
utilized  in  the  trades ;  but  soon  —  at  least  in  some  directions  — 
mutual  relations  presented  themselves,  which  decreased  the 
gap,  at  the  same  time  advancing  both  science  and  the  trades. 
Thus  the  invention  of  the  printing  press  made  it  possible  to 
communicate  one's  thought  or  word  easily  to  all  the  world,  while 
the  invention  of  the  steamboat  and  railroad  brought  people 
in  different  countries  directly  together.  Commerce  became  a 
world  power  and  opened  new  markets.  Competition  started 
and  with  it  came  the  necessity  of  making  improvements. 

In  this  way  in  the  course  of  the  nineteenth  century  modern 
engineering  and  the  technical  sciences  originated,  which  now 
represent  one  of  the  most  influential  factors  in  modern  civiliza- 
tion. But  this  enormous  progress  was  directly  based  upon  the 
correct  practical  application  of  the  natural  sciences. 

Whereas  formerly  science  was  the  foundation  on  which  modern 
engineering  developed,  the  reverse  is  now  often  the  case.  Every 
new  scientific  invention  is  still  carefully  followed  up  by  the 
engineer  and  utilized  for  practical  purposes,  even  more  than  ever 
before.  But  it  often  now  happens  that  the  engineer  promotes 
science  by  making  a  scientific  research  in  order  to  solve  a 
technical  problem. 

This  indicates  what  must  be  demanded  now  of  a  good 
engineer. 

He  must  have  a  thorough  scientific  education  and  must  be 
able  to  work  scientifically  in  unexplored  fields;  he  must  gain 
practical  experience,  which  necessitates  highly  developed  powers 
of  observation,  and  he  must  have  the  faculty  of  utilizing  the 
results  of  science  in  practice.  For  this  purpose  he  must  be  able 
to  think  logically,  scientifically  and  technically,  for  these  two 
requirements  are  by  no  means  identical. 

We  have  seen  above  how  the  trades  were  gradually  trans- 
formed to  modern  industries.  Like  all  great  changes,  this 
transformation  involved  serious  complications;  the  conflict 


4  HEAT  ENERGY   AND  FUELS 

between  capital  and  labor  originated  capitalism  and  socialism. 
Between  capital,  that  makes  the  creation  of  large  industries 
possible,  and  labor,  which  first  of  all  represents  the  producing 
power  in  the  industries,  stands  the  engineer,  the  mental  leader. 
His  is  the  task  not  only  to  keep  up  order  and  discipline  in  the 
enterprise,  but  also  to  act  as  mediator  between  those  two  opposite 
parties.  This  is  not  easy,  nor  pleasant,  but  it  is  a  very  important 
duty.  Its  fulfillment  requires  energy  toward  both  sides,  and 
sometimes  even  apparent  harshness;  but  also  a  good  heart  and 
the  earnest  desire  to  find  out  the  causes  that  are  at  the  bottom 
of  the  endeavors  on  both  sides. 

Every  worker,  including  the  engineer,  who  works  with  his 
intellect,  is  right  in  asking  for  reasonable  wages,  and  it  is  per- 
fectly right  and  proper  that  the  capitalist,  who  lends  his  money 
to  the  enterprise,  should  expect  a  profit  out  of  it.  This  is  the 
main  cause  of  the  conflict.  The  industrial  enterprise  as  such 
must  also  earn  something.  It  is  necessary  to  put  aside  capital 
for  protection  against  unforeseen  events  and  against  menacing 
competition,  for  making  enlargements,  etc.  Every  industry 
must,  therefore,  endeavor  to  make  a  profit.  If  the  management 
of  an  enterprise  is  to  remain  in  the  hands  of  the  engineer  he  has, 
therefore,  to  be  familiar  with  commercial  questions  and  economic 
problems. 

Like  all  others  the  chemical  industry  needs  buildings,  appa- 
ratus, machines,  and  means  of  transportation,  and  the  chemical 
engineer  should  know  something  about  these  mechanical  appli- 
ances, not  only  in  the  interest  of  the  industry,  but  also  to  insure 
him  his  position,  as  otherwise  the  business  management  will  be 
given  into  the  hands  of  a  business  man,  and  the  technical  man- 
agement into  the  hands  of  other  (non-chemical)  engineers. 
This  will  be  especially  the  case  in  places  where  labor  is  scarce 
and  wages  high,  as  it  then  becomes  necessary  to  reduce  the 
operating  expenses  by  the  installation  of  mechanical  appliances. 

Attention  has  to  be  paid  also  to  the  welfare  of  the  working- 
man  by  the  provision  of  baths,  hospitals,  schools,  etc.,  which 
also  requires  special  knowledge. 

Finally  the  engineer  must  have  a  very  important  faculty, 
that  is,  to  keep  cool  in  danger.  This  faculty  has  its  own  com- 
mercial value,  since  on  it  human  lives  often  depend.  Related 
therewith  is  courage,  which  in  moments  of  danger  enables  a 


GENERAL  REMARKS  5 

man  to  be  cautious  and  quick,  to  consider  all  possibilities,  and 
to  act  for  the  greatest  good. 

Much  is,  therefore,  expected  of  an  engineer,  and  the  question 
is,  how  shall  the  chemical  engineer  acquire  all  these  qualities 
and  this  knowledge? 

Coolness  and  courage  are  traits  of  character  that  each  must 
acquire  for  himself;  hence  we  cannot  consider  them  here.  Nor 
can  practical -experience  be  taught  in  a  school,  by  a  teacher  or 
text-book,  since  practical  experience  is  not  the  knowledge  of 
such  facts  as  are  stated  in  technical  text-books,  but  rather  the 
faculty  of  making  proper  use  of  such  facts  in  practice.  This 
faculty  is  best  acquired  in  practice  if  the  eyes  are  kept  open. 
Instruction,  however,  can  help  a  man  to  educate  himself  in 
correct  technical  thinking,  as  we  will  proceed  to  show. 

It  is  the  task  of  the  school  to  give  to  its  students  a  thorough 
scientific  education,  i.e.,  to  give  them,  as  far  as  possible,  a 
thorough  theoretical  foundation.  The  school  must  encourage 
original  research  and  independent  scientific  reasoning;  it  must 
increase  the  powers  of  observation  and  judgment,  and  must 
show  by  concrete  examples  how  scientific  results  are  used  in 
practice. 

But  this  is  not  so  easy  a  task  as  appears  at  first  sight.  First 
of  all  the  data  available  for  lectures  on  chemical  engineering  are 
so  limited  that  it  is  absolutely  impossible  to  discuss  and  treat  in 
detail  all  the  branches  of  the  industry.  Only  such  branches  of 
chemical  engineering  can  be  treated  in  detail  as  are  either  of 
great  industrial  importance  (like  fuels,  combustion,  the  industry 
of  heavy  chemicals,  iron  and  steel  metallurgy,  etc.)  or  those 
branches  which  seem  especially  adapted  to  develop  in  an  engineer 
the  faculties  sketched  above.  Special  stress  is  to  be  laid  on  the 
discussion  of  the  theoretical  basis  of  the  various  processes,  and 
the  discussion  of  apparatus  is  to  be  limited  to  the  most  important 
types.  It  may  frequently  happen  that  such  typical  examples 
are  not  taken  from  latest  practice,  but  from  older  methods  of 
operation,  if  the  latter  show  the  fundamental  process  with 
greater  clearness. 

While  this  principle  also  holds  good  for  the  writing  of  a  text- 
book on  chemical  engineering,  we  are  permitted  to  cover  a  wider 
field;  for  limitation  in  the  selection  of  the  various  industries  is 
not  as  essential  as  in  lectures.  However,  even  a  text-book,  the 


6  HEAT   ENERGY  AND  FUELS 

object  of  which  is  first  of  all  to  supplement  lectures,  should  not 
be  too  voluminous. 

Compared  to  a  book  the  personal  lecture  has  a  great  advantage, 
in  that  the  teacher  can  observe  from  the  attentiveness  of  his 
students  whether  he  is  understood;  and  if  not  he  can  explain 
his  subject  more  in  detail.  A  text-book  can,  therefore,  never 
entirely  replace  the  lecture,  but  may  be  very  useful  in  supple- 
menting it. 

However,  neither  lecture  nor  text-book  alone  can  accomplish 
the  same  ends  as  university  or  college  instruction,  since  the  latter 
has  two  additional  aids  in  excursions  and  laboratory  work. 
The  latter  should  not  be  limited  to  analytical  work;  on  the  con- 
trary the  student  ought  to  be  a  good  analyst  when  he  starts  to 
work  in  the  chemical  engineering  laboratory.  Naturally  he  has 
to  do  analytical  work  also  in  this  period,  but  this  should  not  be 
his  principal  work.  In  this  stage  synthetic  work  should  be  kept 
in  the  foreground,  with  solutions  of  problems  such  as  may 
actually  occur  in  practice ;  it  is  even  advisable  that  the  students 
learn  to  design  plants  and  to  make  critical  reports  on  designs 
which  have  been  worked  out. 

This  goes  far  beyond  the  ordinary  limits  of  chemical  engineer- 
ing instruction  and  increases  the  work  of  the  teacher;  but  it 
brings  valuable  results.  This  kind  of  instruction,  however,  is 
very  difficult  in  the  ordinary  laboratories  and  necessitates  the 
installation  of  special  technological  schools.  Their  erection 
would  simultaneously  amend  another  defect  of  present  methods 
of  instruction.  As  above  mentioned,  instruction  as  given  now 
cannot  but  be  encyclopedical  and  is  very  far  from  being  a 
thorough  technical  education.  This,  however,  can  be  remedied 
by  giving  the  students  in  special  schools  an  opportunity  to 
acquaint  themselves  more  in  detail  with  a  limited  field  of  chemical 
engineering  according  to  their  choice  —  without  changing  the 
present  encyclopedic  instruction  in  the  whole  engineering  field. 

Excursions  are  also  an  important  means  of  instruction,  as 
the  student  has  a  chance  to  see  actual  industrial  works,  and  to 
observe  operations  carried  out  on  a  large  scale.  If  they  are  to 
be  useful  and  profitable,  a  number  of  conditions  should  be 
fulfilled.  The  number  of  the  participants  should  not  be  too 
great;  if  the  number  of  the  students  is  very  large  they  must  be 
divided  into  several  parties.  At  first  only  short  excursions 


GENERAL  REMARKS 


should  be  made  to  stimulate  the  faculty  of  observation  of  the 
students.  An  excursion  must  not  be  made  before  the  processes 
used  in  the  works  to  be  visited  have  been  discussed  in  the  lectures. 
Interest  in  excursions  and  resorption  of  the  things  observed 
are  increased  by  exercises  in  designing,  and  by  working  out 
projects,  as  we  have  already  mentioned.  It  would  also  be 
advantageous  if  a  professor  of  mechanical  engineering  would 
participate  in  these  visits.  Such  excursions  should  be  aided  and 
facilitated  by  the  government,  railroads  and  manufacturers.  It 
hardly  requires  mentioning  that  a  well  arranged  museum  or 
collection  of  things  of  technical  interest  is  also  of  great  assistance 
in  instruction. 

If  we  now  turn  to  our  subject  proper  —  chemical  technology  — 
we  find  it  difficult  to  define  exactly  the  word  " technology." 

The  name  of  our  science,  literally  translated,  means  "  disci- 
pline of  the  arts"  (r^V,  Aoyos).  So  we  might  conclude  to 
define  as  technology  the  mechanics  of  all  possible  arts,  from  all 
the  fine  arts  to  the  handicrafts.  This,  however,  is  not  the  case, 
as  neither  the  fine  arts  and  handicrafts  nor  agriculture  and 
mining  belong  to  the  sphere  of  technology. 

On  the  other  hand,  in  various  trades,  which  are  not  included 
in  engineering  science,  the  same  appliances  and  methods  are 
used  as  in  engineering. 

The  problem  becomes  even  more  complicated  if  we  keep  in 
mind  that  in  technical  processes  not  only  substances  are  trans- 
formed but  also  energies  so  as  to  assume  a  more  useful  and  more 
convenient  form. 

We  could,  therefore,  define  technology  as  the  science  of  the 
methods  by  which  materials  and  forms  of  energy  as  we  find  them 
are  transformed  so  as  to  become  more  useful  and  valuable. 

To  what  extent  the  value  of  a  substance  is  increased  by  the 
work  of  the  engineer  is  shown  by  the  following  example,  taken 
from  a  paper  of  the  English  ironmaster,  Ldwthian  Bell : 


Scale  of  Iron. 

Price  per  Kg. 

Scale  of  Iron. 

Price  per 
Kg. 

Pig  iron 

0  01 

Needles  from  same 

1  3 

Rail-steel 

0  014 

Fine  wire 

1  4 

Gas-pipes  
Bessemer  steel  
Bessemer  steel  wire  

0.02 
0.02-0.025 
0.3 

Fine  needles  from  same  . 
Chronometer  springs  .... 
Finest  watch-springs.  .  .  . 

1.68 
3.00 
2000.00 

8  HEAT   ENERGY  AXD  FUELS 

The  transformation  of  substances  and  energies  always  requires 
a  certain  amount  of  work  and  always  involves  the  practical  loss 
of  a  fraction  of  the  substance  or  energy. 

To  carry  out  the  desired  transformation,  it  is  necessary  to 
install  a  plant  with  buildings  and  proper  appliances,  such  as 
machines,  furnaces,  etc.  The  running  (operating)  expenses  are 
calculated  as  follows: 

(a)  First  cost  of  plant  (to  be  depreciated). 

(b)  The    operating    expenses    proper    (wages,    cost    of    raw 
materials,  transportation,  taxes,  etc.). 

(c)  Reserves  for  protection  against  all  emergencies. 

On  the  other  hand,  the  unavoidable  loss  of  material  and  energy 
in  every  process  means  a  loss  of  capital  and  an  increase  of  the 
operating  expenses. 

For  effecting  the  greatest  possible  economy  all  these  expenses 
and  losses  have  to  be  reduced  to  a  minimum. 

The  reduction  of  the  first  cost  and  operating  expenses  depends, 
first  of  all,  on  the  methods  used;  and,  generally  speaking,  the 
method  of  operation  will  be  the  more  economical 

1.  The  lower  the  first  cost  (capital  invested). 

2.  The  cheaper  the  labor  and  the  raw  material  used. 

3.  The  quicker  the  working  (which  means  careful  planning). 

4.  The  more  convenient  the  location  (with  respect  to  labor 
market  and  shipping  facilities). 

5.  The  smaller  the  loss   of  raw  material  and  energy.    In 
this  respect  a  method  can  be  made  profitable  in  many  cases  by 
utilizing  again  the  losses  (at  least  partly)  either  by  using  them 
again  in  the  same  process  or  by  converting  them  into  marketable 
by-products. 

6.  The  quality  and  the  selling  price  of  the  finished  product 
are  naturally  also  of  the  greatest  importance. 

The  object  of  a  process  can  be  of*two  different  kinds: 
The  object  may  be,  for  instance,  a  change  of  form  (disinte- 
gration, agglomeration 'into  larger  pieces,  change  of  shape)  or  a 
mechanical  separation  into  products  of  different  values.  In  the 
case  of  energies  the  object  may  be  to  transform  them  into  use- 
ful forms.  This  is  the  case  in  utilizing  the  energy  of  a  water- 
fall or  of  the  wind  by  means  of  water-wheels  and  wind-mills; 
or  in  the  change  of  certain  forms  of  energies  into  others,  as  in 


GENERAL  REMARKS  9 

electric  generators.  The  science  that  treats  on  these  subjects 
is  mechanical  engineering. 

Secondly,  the  object  may  be  to  transform  raw  materials  by 
chemical  changes  into  substances  of  a  different  chemical  com- 
position, or  to  transform  chemical  energy  into  other  forms  of 
energy  (mechanical  energy,  heat,  light  and  electricity).  All 
such  processes  are  in  the  sphere  of  chemical  engineering. 

Both  branches  of  technology,  however,  are  so  closely  related 
that  it  is  impossible  to  draw  a  sharp  line  between  the  two. 
The  manufacture  of  paper,  for  instance,  and  iron-foundry  work 
is  frequently  treated  in  text-books  of  both  mechanical  and 
chemical  engineering,  while  the  purification  of  sulphur  occurring 
in  nature  and  of  the  native  metals  is  often  described  only  in 
chemical  works,  notwithstanding  the  fact  that  only  mechanical 
and  physical  processes  are  involved. 

The  chemical  engineer  has  to  use  frequently,  besides  chemical, 
also  mechanical  means,  and  in  many  cases  he  has  to  be  well 
informed  as  to  water-wheels,  steam-engines,  blowers,  pumps,  etc. 
Mechanical  and  chemical  changes  are  often  so  closely  combined 
(as  in  annealing  sheet  metals,  welding  of  iron,  hardening  of  steel, 
etc.),  that  a  correct  idea  of  the  respective  processes  can  only  be 
formed  from  a  chemical-mechanical  point  of  view. 

According  to  these  explanations  chemical  technology  can  be 
divided  into  two  main  groups : 

1.  Chemical  technology  of  the  energies. 

2.  Chemical  technology  of  materials. 

This  book  will  treat  of  the  first. 

In  the  chemical  technology  of  materials  use  must  be  made  of 
energy  for  forming  the  desired  products,  while  in  the  chemical 
technology  of  energies  materials  must  be  employed  as  carriers  of 
chemical  energy.  No  strict  division  can  therefore  be  made 
between  these  groups,  but  it  presents  many  advantages  for 
instruction. 

We  therefore  comprise  under  "  chemical  technology  of  the 
energies"  the  science  of  the  change  of  chemical  into  other  forms 
of  energy  and  will  consider  the  transformation  of  chemical  energy 
into 

(a)  Heat  (by  combustion,  generated  or  consumed  by  other 
chemical  processes;  firing  and  refrigeration). 


10  HEAT   ENERGY  AND  FUELS 

(6)  Mechanical  energy  (explosives  and  internal  combustion 
engines). 

(c)  Radiant  energy  (mainly  light,  i.e.,  chemical  illumination; 
transformation  into  heat-rays  is  considered  under  a). 

(d)  Electricity  (galvanic  cells  and  storage  batteries). 

Especially  in  the  case  of  production  of  heat  from  fuel,  and  in 
the  case  of  explosives  and  illuminants,  it  is  hardly  possible  to 
separate  chemical  technology  of  energies  from  the  materials 
that  furnish  the  chemical  energy  to  be  transformed,  so  that 
we  will  find  it  necessary  to  consider  also  the  technology  of  these 
materials. 


CHAPTER  II. 
FORMS  OF  ENERGY. 

ENERGY  is  the  power  to  do  work,  if  we  call  work  a  change 
of  state  in  general. 

The  performance  of  all  our  industrial  operations  requires  a 
considerable  amount  of  energy,  for  instance,  mechanical  energy 
in  the  working  of  metals,  disintegrating  of  phosphates,  cements, 
and  other  raw  materials  for  conveying  and  transporting 
materials;  heat  energy  for  melting  metals  and  burning  of  lime, 
cement  and  ceramic  products;  electric  energy  for  illuminating, 
refining  of  copper,  production  of  aluminum  and  chlorine;  light 
energy  for  illuminating  and  photography;  chemical  energy  in 
the  production  of  chemical  compounds,  as  chlorate  of  potash, 
explosives,  etc. 

Energy  cannot  be  made  from  nothing,  but  has  to  be  procured 
from  the  natural  reservoirs  of  energy  in  which  it  is  accumu- 
lated. We  are,  however,  enabled  to  draw  from  the  accumu- 
lated energies  of  nature,  and  by  means  of  certain  machines  to 
transform  them  into  other  forms  of  energy,  but  without  increas- 
ing the  total  amount.  This  is,  for  instance,  done  in  steam 
engines,  electric  generators  and  batteries,  etc. 

Of  the  natural  reservoirs  of  energy,  the  following  are  of 
industrial  importance : 

1.  Live  motors  (man,  horse,  etc.). 

2.  Falling  water  (waterfalls,  creeks,  rivers). 

3.  Moving  air  (wind  motors  and  sailing  vessels). 

4.  Substances   in   which   chemical   energy   is   stored.     The 
.most  important  of  these  are  the  fuels. 

All  these  available  sources  of  energy  are  actually  only  inter- 
mediate reservoirs,  their  energy  having  been  obtained  from  the 
sun  in  a  more  or  less  direct  way.  The  sun  is,  therefore,  the 
original  source  of  all  energy,  of  all  heat,  of  all  electric  energy 
and  of  all  chemical  phenomena  on  the  surface  of  the  earth. 

11 


12  HEAT  ENERGY  AND  FUELS 

The  sun  transmits  energy  to  the  waterfalls  by  heating  and 
evaporating  sea  water;  transmits  energy  to  all  plants  by  decom- 
posing the  carbon  dioxide  of  the  air  by  means  of  its  rays,  trans- 
forming the  plants  in  the  ground  into  fossil  coal. 

It  is  evident  that  by  this  transmission  a  large  amount  of  solar 
energy  is  lost.  We  have  to  add,  for  instance,  to  the  water  for 
evaporation  the  total  latent  evaporating  heat,  which  is  again 
liberated  by  the  condensation  to  liquid  water  and  a  large  part 
of  the  water  condensed  in  the  mountains  cannot  be  utilized, 
partly  on  account  of  practical  reasons,  partly  on  account  of  its 
seeping  into  the  ground,  and  partly  on  account  of  the  evapora- 
tion on  its  downward  way;  therefore  the  experiments  for 
directly  utilizing  the  radiant  energy  of  the  sun  deserve  our 
most  earnest  consideration.  Precisely  speaking,  however,  all 
these  losses  are  only  losses  to  the  industrial  world  and  not 
to  the  earth,  as,  for  instance,  by  the  condensation  of  water- 
vapor,  the  air  layers,  in  which  this  phenomenon  takes  place,  are 
warmed  up. 

The  radiant  energy  of  the  sun  is,  therefore,  the  only  source 
from  which  the  energy-content  of  our  earth  can  be  increased, 
and  the  radiation  of  the  earth  is  the  only  source  of  energy- 


Before  going  into  the  details  of  the  chemical  technology  of 
energies  it  might  be  well  to  say  a  few  words  about  the  differ- 
ent forms  of  energy. 

All  possible  changes  occurring  in  a  system  can  be  referred 
to  three  fundamental  quantities:  The  mass  (M),  the  space, 
which  can  be  conceived  as  the  cube  of  length  or  distance  (L3), 
and  the  time  (T).  All  these  changes  can  be  reduced  to  changes 
of  energies  and  we  can  therefore  measure  all  forms  of  energy 
by  using  as  units  mass,  distance  and  time. 

If  we  allow  a  system  to  go  through  certain  changes  without 
adding  or  deducting  energy,  so  that  it  returns  again  to  the 
first  state,  then  the  system  contains  again  the  same  form  and 
the  same  quantity  of  energy  as  in  the  beginning.  Energy 
cannot  be  lost  or  generated,  but  only  transformed  into  other 
forms. 

The  mathematical  expressions  for  all  forms  of  energy  can  be 
divided  into  two  factors,  the  capacity  factor  and  the  intensity 
factor.  The  former  is  more  or  less  unchangeable,  while  on  the 


FORMS  OF  ENERGY  13 

latter  depends  the  equilibrium.  Equilibrium  between  two 
quantities  of  energy  is  only  attained  when  the  intensities  are 
equal.  If  we  indicate  the  energy,  intensity  factor  and  capacity 
factor  with  E,  I  and  c,  respectively,  we  have 


and  therefore  dE  =  Idc  +  cdi; 

dE 

it  c  is  constant  we  have         —  =  c: 

di 

if  i  is  constant  we  have        -—  =  i. 

dc 

This  defines  exactly  the  nature  of  these  energy  factors. 
The  following  are  the  known  forms  of  energy  : 

1.  Mechanical  energy. 

2.  Heat. 

3.  Electric  and  magnetic  energy. 

4.  Chemical  energy. 

5.  Radiant  energy. 

1.   Mechanical  energy  occurs  in  the  following  forms: 

(a)  Kinetic  or  actual  energy. 

(6)  Energy  of  space,  which  can  be 

(1)  Energy  of  distance. 

(2)  Energy  of  surface. 

(3)  Energy  of  volume. 

(a)  The  mathematical  expression  for  kinetic  energy  is 


According  to  the  way  by  which  this  expression  is  split  into 
factors  we  get  as  capacity  factor  either  m,  which  quantity  is 
absolutely  unchangeable,  or  mv,  which  is  only  relatively 
unchangeable,  while  as  factor  of  intensity  we  obtain  half  the 

square  of  velocity  f  —  J  or  the  velocity  itself  (v). 

The  unit  of  kinetic  energy  is  the  Erg  (E),  which  is  the 
energy  contained  in  the  mass  of  a  gram,  when  moving  with  a 


14  HEAT   ENERGY  AND  FUELS 

velocity  of  1  centimeter  per  second.     The  dimension  of  the 
kinetic  energy  (expressed  by  M,  L  and  T),  is 


The  energy  of  space  occurs  in  three  different  forms  in  which 
the  capacity  factor  is  represented  by  distance,  surface  and  vol- 
ume respectively.  We  have 

Form  of  energy.  Capacity.  Intensity. 

Energy  of  distance  =  distance  X  force 

Energy  of  surface    =  surface  (area)  X      tension 
Energy  of  volume    =  volume  X  pressure. 

The  energy  of  distance  acts  between  two  points  in  the  direc- 
tion of  their  connecting  line.  If  we  indicate  the  length  (dis- 
tance) with  I  and  the  force  with  /,  we  have 

E  =  If,  and  therefore  the  force 

a 

3    di 

is  equal  to  the  ratio  of  change  of  energy  to  change  of  distance 
(length).  If  the  energy  of  distance  is  transformed  exclusively 
into  kinetic  energy  (as  in  the  ordinary  mechanical  and  astro- 
nomical problems)  this  equation  expresses  the  acceleration,  a, 
and  then  corresponds  to  the  ordinary  definition  of  force. 

The  energy  of  surface  is  active  on  the  surface  of  liquids  and 
solids.  Its  intensity  of  factor,  the  tension,  is  identical  with  the 
constant  of  capillarity. 

The  energy  of  volume  appears  in  gases.  Its  factors  are  volume 
and  pressure. 

We  have,  therefore,  the  following  expressions  for  the  dimen- 
sions of  the  energies  of  space  and  its  factors : 

Capacity.  Intensity.  Energy. 

distance  (L)  force         =  [EL~l]  E 

surface  (L2)  tension    -  [EL~2]  E 

volume  (L3)  pressure  -  [EL~3]  E 

We  know  of  two  kinds  of  energy  of  distance,  one  of  which 
(called  gravity)  acts  between  two .  material  points  so  that  the 


FORMS  OF  ENERGY  15 

energy  increases  with  the  distance  and  reaches  a  minimum 
when  the  points  are  in  direct  contact.  It  is  governed  by 
Newton's  law  of  gravitation.  If  we  indicate  the  energy  of  dis- 
tance with  Ed,  the  two  masses  acting  upon  each  other  with  m 
and  m2,  their  distance  with  r,  we  can  express  this  law  by  the 
equation 


in  which  ct  and  j2  are  constants.  If  r  =  GO  and  Ed  =  cv  it 
reaches  a  maximum.  The  differential  of  this  equation  gives 
us  the  ordinary  form  of  this  law  : 

dE  .  mn 


The  quantity  ct  is  unknown;  the  second  constant  k2  is, 
expressed  in  the  centimeter-gram-second  system, 

j2  =  6.6  X  10-8. 

On  the  surface  of  the  earth  the  force  of  gravity  can  be  con- 
sidered constant  for  moderate  altitudes,  and  the  energy  of  dis- 
tance is  directly  proportionate  to  the  altitude. 

The  second  kind  of  distance  energy  occurs  for  instance  in 
electrically  charged  balls,  and  is  distinguished  from  the  former 
by  reaching  its  maximum  value  at  infinitely  small  instead  of 
infinitely  large  distance  between  the  bodies  acting  upon  each 
other.  For  this  energy  we  have 

E  =  j2  —   —  ,  and  for  the  force 

dE  .  m^n., 

Tr  =     ~  h    r* 

This  force  has  therefore  the  same  formula  as  in  the  first  case, 
but  is  negative.  While  the  gravity  is  an  attracting  force,  this 
force  is  repulsive. 

We  have  seen  above  that  two  masses  acting  upon  each  other, 
under  the  influence  of  gravity,  tend  to  approach  each  other; 
whereby  the  distance  energy  is  decreased,  being  partly  trans- 
formed into  kinetic  energy. 


16  HEAT   ENERGY  AND  FUELS 

The  decrease  of  distance  energy,  corresponding  to  a  decrease 
in  I  of  dl  is 


If  we  suppose 

rax  =  M  mass  of  the  earth  and  m2  =  m  mass  of  a  falling 
body,  r  =  R  the  radius  of  the  earth  and  dr  =  dh  is  an  incre- 
ment of  the  fall-distance,  corresponding  to  an  infinitely  small 
change  of  distance  energy,  we  have 

.  M  .  Mm 

dEd  =  j2  —  m  ah,  an  expression  wherein  j2  ——-  =/  (gravity). 
ri  ti 

Thence  we  can  write 

dEd  =  fdh. 

As  the  lost  distance  energy  is  completely  transformed  into 
kinetic  energy  of  the  equation  dEk  =  mv  dv  we  can  make  both 
expressions  equal  : 

fdh  =  mv  dv. 

By  integration  between  o  and  h  and  o  and  v  respectively  we 
obtain 


rh  rv 

fj  dh  =  m  J   v  dv  or 


//i  =  -  -  ,  as  the  fundamental  law  for  the  mutual  transforma- 

Zi 

tion  of  kinetic  and  distance  energy. 

If  we  put  into  fdh  =  mv  dv  for  the  acceleration  the  value 

v  =  -  -  .  we  get  Galileo's  law  of  fall : 
at 

fdt  =  m  dv,  or 

dv  ^l 

dt       m 

Equilibrium  between  kinetic  energy  and  distance  energy  can 
only  exist  if  the  two  masses,  acting  upon  each  other,  are  moving 
around  their  common  center  of  gravity. 

Analogous  to  the  two  kinds  of  distance  energy  we  can 
imagine  two  kinds  of  surface  energy;  however,  we  know  only 
one  of  them,  i.e.,  the  one  that  tends  to  decrease  the  surface. 


FORMS  OF  ENERGY  17 

The  cause  of  this  is  called  tension  (y).    <r  being  the  surface,  we 
have 

dE 


which  quantity  is  identical  with  the  capillary  constant.  The 
surface  tension  is,  down  to  very  thin  layers,  independent  of  the 
thickness  of  same,  is  proportional  to  the  surface,  and  is  depend- 
ent on  the  temperature  and  on  the  nature  of  the  substances 
separated  by  the  surface. 

A  peculiar  property  of  the  surface  energy  is  that  changes  in 
its  value  are  accompanied  by  changes  of  heat  energy.  If,  for 
instance,  a  soap  bubble  is  increased  by  blowing,  the  surface 
energy  increases  more  than  would  correspond  to  the  mechanical 
energy  used  in  blowing,  the  heat  content  decreases  by  a  cor- 
responding amount,  or,  if  the  temperature  is  kept  constant,  the 
requisite  heat  has  to  be  added  from  the  outside.  During  the 
contraction  of  the  bubble  the  entire  amount  of  the  disap- 
pearing surface  energy  cannot  be  transformed  into  mechanical 
energy,  since  as  much  heat  energy  is  again  produced  as  was 
tranformed  into  surface  energy  during  the  first  process. 

Phenomena  of  equilibrium  between  surface  energy  and  energy 
of  gravitation  occur  in  the  rise  of  liquids  in  narrow  tubes,  g 
being  the  weight  of  the  raised  liquid  and  dh  the  elevation  to 
which  corresponds  the  infinitely  small  decrease  of  the  surface, 
we  have  for  the  equilibrium 

Y  dcr  =  g  dh. 

As  the  decrease  of  the  surface  (do)  must  equal  the  product  of 
the  tangent-line  (u)  and  the  change  of  height  (dh), 

da-  =  u  dh, 
we  have  fu  =  g, 

i.e.,  the  weight  lifted  equals  the  product  of  surface-tension  and 
tangent-line. 

For  the  intensity  factor  of  the  volume-energy  we  have  the 
expression 

dE 


18  HEAT   ENERGY   AND   FUELS 

Of  the  two  possible  kinds  of  volume-energy  only  that  is  of  prac- 
tical importance  which  decreases  with  increasing  volume. 

If  a  gas  or  vapor  is  given  off  from  a  solid  or  liquid  substance 
at  constant  temperature  and  constant  pressure,  we  have 

Ev  =  C  -  p  (v  -  Vo), 
or,  considering  only  the  volume  of  the  gas  formed, 

In  this  equation  for  one  mol  of  all  gases  C  =  RT,  which 
quantity  is  known  from  the  gas-equation. 

For  an  infinitely  small  change  of  volume  of  gases  at  constant 
pressure  we  have 

dEv-=  -  pdv. 
From  the  equation 

pv  -  RT, 

RT  . 

P  —  ~~  > 

therefore  -  dEv  =  RT  — , 

v 

and  -£, -fi    [T  -, 

J        v 

or,  for  constant  temperature, 

-  E,,  =  RT  S~ 

J       y 

By  integration  between  vl  and  v2  we  get 

RTlog1-  =  E/  -  E,!'. 
*'i 

There  is  little  known  of  the  relation  between  volume-energy, 
volume,  and  pressure,  except  in  the  case  of  gases. 

For  the   equilibrium   between  volume   and   distance   energy 
such  as  takes  place,  for  instance,  in  a  cylinder  filled  with  gas,  in 


UNIVER: 

H  L. !  PC f 

FORMS  OF  ENERGY  19 

which  a  pressure  is  exerted  upon  the  gas  by  a  piston  working 
without  friction,  we  have 

j  dh  =  p  dv. 
The  cross  section  of  the  cylinder  being  q, 

dv  =  q  dh, 
then  pq  =  f, 

i.e.,  the  force  equals  the  product  of  gas-pressure  and  cross- 
sectional  area. 

Before  mentioning  the  other  forms  of  energy  we  want  to 
consider  a  few  general  important  considerations. 

If  there  is  no  equilibrium  in  a  system  between  the  forms  of 
energy  present,  the  system  is  undergoing  a  change  so  that  the 
decrease  of  one  form  of  energy  is  greater  than  the  increase  of 
the  other.  Then  energy  goes  over  from  places  of  higher  inten- 
sity to  those  of  lower  intensity  whereby  it  is  sometimes  trans- 
formed into  other  forms  of  energy;  to  what  extent  such  a 
transformation  takes  place  depends  on  the  nature  of  the  system, 
which  —  inasmuch  as  it  effects  a  transformation  of  energy  —  is 
called  a  machine. 

In  the  above  supposed  case  of  unbalanced  energy  the  neces- 
sary change  of  state  of  the  system  can  take  place  in  various 
ways.  A  lifted  stone,  for  instance,  can  fall  vertically  to  the 
earth  or  can  slide  down  an  inclined  plane.  It  will  select,  in 
fact,  the  way  along  which  it  attains  in  the  same  length  of 
time  the  greatest  possible  kinetic  energy.  The  generalization 
of  this  principle  is:  Of  all  possible  transformations  of  energy 
the  one  will  take  place  that  will  produce  in  a  given  time  the 
largest  transfer  of  energy  from  the  original  form  to  some 
other. 

2.  Heat  was  the  first  form  of  energy  to  be  recognized  as  an 
independent  quantity.  In  connection  with  this  form  of  energy 
two  important  laws  were  formulated,  which  laws  also  hold  for 
all  the  other  forms  of  energy : 

(a)  Thermodynamic  law:  Heat  can  be  transformed  into 
mechanical  work  and  other  forms  of  energy  and  vice  versa. 
This  transformation  takes  place  according  to  certain  definite 


20  HEAT  ENERGY  AND  FUELS 

laws.  This  law  is  based  upon  the  fact  that  energy  cannot  be 
made  nor  destroyed,  but  only  transformed  from  one  form  into 
another.  Clausius  has  formulated  this  same  law  as  follows: 
the  energy  of  the  universe  is  constant. 

(b)  Thermodynamic  law:  Heat  cannot  go  of  its  own  accord 
from  a  colder  to  a  warmer  body.  Applying  this  law  to  all 
forms  of  energy  we  can  say:  If  two  bodies  are  in  equilibrium 
with  a  third  with  respect  to  certain  forms  of  energy,  they  are 
also  in  equilibrium  with  each  other  as  regards  the  same  forms  of 
energy. 

If  we  add  to  a  body  the  heat  dQ  at  the  absolute  temperature 
T,  we  have 

/  —  ^=0  (=  for  reversible,  <  for  non-reversible  processes). 

The  second  law  has,  furthermore,  another  important  meaning. 
In  a  reversible  process,  carried  out  between  very  narrow  limits 
of  temperature  (between  T  and  T  +  dt),  the  heat  quantity 
added  to  the  system  being  Q,  the  infinitely  small  part 


of  this  added  heat  can  be  transformed  into  work  or  other  forms 
of  energy.  This  is  a  law  of  special  importance  in  the  study  of 
energy.  As,  according  to  above  explanation,  we  have  for 

reversible  processes  /  —  =  0,  —  must  be  the  total  differential 
*J    1  1 

of  a  quantity  which  —  just  as  the  energy  —  depends  only  on 
the  state  of  the  body,  but  not  on  the  way  by  which  this  state 
was  reached.  Clausius  calls  this  quantity  "entropy,"  and  it  is 
generally  denoted  by  s,  and  by  introducing  this  quantity  into 
the  second  principle  we  get 

dQ  =  T  ds. 

Like  all  other  forms  of  energy  the  heat  can  be  decomposed 
into  two  factors,  one  of  intensity  and  the  other  of  capacity. 
The  former  is  the  temperature,  while  the  latter,  according  to 
circumstances,  is  represented  by  the  entropy  or  heat-capacity. 


FORMS  OF  ENERGY  21 


The  general  equation  of  energy  being 

E  =  ci, 
and  the  total  differential 

dE  =  c  di  +  idc 
we  have  for  a  constant  c  (dc  =  0)  ; 

dE 

j.    —  c, 
di 

and  for  constant  i  (di  =  0) 


For  the  heat  we  have  i  =  T.  If  we  add  to  a  substance  the  heat 
quantity  dQ,  so  that  no  other  form  of  energy  is  generated  (with- 
out being  considered)  and  if  we  determine  the  relation  between 
the  heat  added  and  the  increase  of  temperature  effected 
thereby,  we  have 

dE  =  c  dt, 

wherein  c  stands  for  the  heat  capacity  of  the  substance. 

In  melting  and  evaporation  and  solidifying  or  condensation 
respectively,  and  also  in  many  chemical  processes  taking  place 
at  constant  temperature  we  have 

dE  =  dcT 

or  analogous  to  the  former  equation 

dE  =  dsT. 

The  total  values  of  the  entropy  being  unknown  we  have  to 
transform  these  equations  by  referring  them  to  two  states 
marked  by  index  1  and  2  : 

(s,  -  s2)  dT  =  (c,  -  ca)  di. 

We  have,  for  instance,  assuming  equilibrium  between  heat 
and  volume-energy, 

(«!  -  s2)  dT  =  (^  -  v2)  dp, 
or, 

sl  —  s2      dp 
v,  -v^df' 


22  HEAT   ENERGY   AND   FUELS 

If  we  indicate  the  latent  heat  of  the  process  referred  to 
(chemical  reaction,  etc.)  by  I  we  have 

I 


and  therefore 


which  expression  is  correct  for  all  changes  of  the  state  of  aggre- 
gation and  all  chemical  changes  of  state,  that  are  connected 
with  a  change  of  volume.  We  can  transform  it  into 

7  /7T7 

—  —    =  (vl  -  v2)  dp  (Clapeyron's  equation). 

4.  As  coefficient  of  capacity  of  chemical  energy  the  gram- 
atom  of  the  elements  or  the  gram-molecule  is  generally  used, 
while  as  coefficient  of  intensity  the  "  chemical  potential  "  or 
simply  "  potential  "  is  used  (J.  Willard  Gibbs).  For  the  latter 
quantity  we  have,  according  to  the  general  energy-equation, 

dE 

%  = 


dc 

The  individual  values  of  the  quantities  of  chemical  intensity 
being  unknown,  we  can  only  consider  their  sum  as  appearing 
in  equations  of  chemical  reactions.  If,  for  instance,  El  and  E2 
represent  the  total  chemical  energy-content  of  a  system  in  the 
beginning  and  end  state  respectively,  q  being  the  energy  gen- 
erated (liberated)  in  going  from  1  to  2,  we  have 


If  we  divide  now  both  sides  of  the  equation  by  the  capacity 
c  of  the  system  (c  remaining  constant  in  the  processes  under 
consideration)  we  get 

fi.fiys, 

c         c        c 


or,  i,  =  i2  +  -  - 


FORMS  OF  ENERGY  23 

As  the  capacity  c  is  always  a  positive  quantity  we  have, 
if  q  =  0  -  ^  =  i2;  it  >  i2  if  q  >  0  and  ^  <  i2  if  q  <  0. 
Thence  chemical  equilibrium  can  only  take  place  if  the  inten- 
sities of  the  forms  of  chemical  energy  before  and  after  the 
transformation  are  equal;  otherwise  —  if  this  is  possible  —  such 
a  transformation  will  take  place  that  the  intensity  decreases 
(and  on  account  of  the  equality  of  the  capacities  the  total 
chemical  energy  of  the  system  will  also  decrease). 

If  instead  of  one  single  chemical  substance,  as  in  the  case 
above,  there  are  several,  it  must  be  remembered  that  to  every 
one  of  them  there  corresponds  a  certain  quantity  of  chemical 
energy  and  also  of  intensity,  so  that  we  can  write  an  energy- 
equation  for  every  substance.  If  we  go  back  to  the  ele- 
ments, i.e.,  to  the  individual  kinds  of  atoms  present,  and 
mark  their  number  before  and  after  the  transformation  with 
n/,  n2,  n3'  .  .  .  and  n/',  n2",  na",  .  .  .  ,  respectively,  their 
energy  content  with  #/,  E2',  E3',  .  .  .  ,  #/',  EJ',EJft  and  the 
energy  of  reaction  connected  with  the  transformation  with 
q',  q" ',  q'",  we  have,  for  every  kind  of  atom, 

<£/  =  <    (£/  +     q), 


w" 


(1) 
or,  for  every  single  atom, 

/  77T   /          i        _.   / 

L       =    ^2        +    ffl  I 
''    =    7?  ".  4-   n" 

(2) 


E»  =  E^  +  q", 


We,  therefore,  get   the    following   expression  for   the   total 
reaction  : 

<#/  +  n^E,  '  +  ...=  n2'E2'  +  n2"E2"  .  .  . 

+  q'  +  q"  +  ....  (3) 

By  an  analogous  method  we  get  for  the  capacities 

or,  as  according  to  the  above  explanation  n^  =  n2;  n"  =  n2", 
etc.,  n/c/  +  n/'c/'  +  •  •  •  =  «  +  n/'c/'-  (4a) 


* 

24  HEAT  ENERGY  AND  FUELS 

If  we  divide  each  of  the  equations  (2)  with  the  correspond 
ing  capacity  value,  we  get  the  intensity-equation 


(5) 


and  therefore  for  the  total  reaction 


It  is  necessary  that  for  the  equilibrium  i{  +  t/'  +  .  .  .  = 
V+V  +  •  •  •  and  tnis  is  only  possible  if  ^  -  =0,  i.e.  if  2}g  =  0. 

Now  we  can  arrange  the  intensities  corresponding  to  the 
original  and  final  systems  so  that  they  correspond  to  the  dif- 
ferent compounds  appearing  in  the  reaction-equation;  if  we 

also  sum  up  the  quotients  -  and  distinguish  by  index  the  sums 

c       , 

of  intensities   corresponding  to  every  substance,  we   get  the 
expression 


For  equilibrium  2J  -  **  0, 

It  could  be  thought  from  the  above  explanation  that  the 
energy  of  reaction  of  a  reaction  represents  directly  the  change 
of  the  chemical  energy  of  the  system,  when  passing  from  the 
original  to  the  final  state.  This  conclusion,  however,  would  be 
incorrect,  since  not  only  the  chemical  but  also  all  the  other 
forms  of  energy  contained  in  the  system  are  undergoing  a 
change  during  the  transformation.  But  we  can  go  a  little 
further  in  the  case  of  chemical  equilibrium,  since  in  this  case 
the  intensities  of  the  original  and  final  system  must  have 
become  equal,  and  since  the  capacity  of  the  system  must 


FORMS  OF  ENERGY  25 

remain  constant  during  the  transformation,  the  amounts  of  the 
various  forms  of  energy  also  must  be  equal  to  each  other.  In 
the  case  of  the  equilibrium,  therefore,  the  heat-force  of  a 
reaction  measures  the  distance  of  the  non-chemical  energy 
values  before  and  after  the  reaction. 

For  ascertaining  the  changes  of  chemical  energy  of  a  system 
when  passing  from  one  state  to  another,  we  can  start  from  the 
energy  of  reaction  accompanying  this  change  of  state,  consid- 
ering also  the  changes  that  the  other  forms  of  energy  are  under- 
going. As  such  we  find  mainly  the  heat  and  the  energy  of 
volume,  which  will  be  better  understood  by  the  following 
example. 

The  reaction 

H,  +  J  (02)  =  HjO 

takes  place  with  generation  of  heat.  The  quantity  of  this 
energy  of  reaction  is  calculated  by  means  of  KirchhofFs  law  as 
follows : 

QT  =  58,294.6  +  3.25  T  -  0.002  T\ 

If  the  combustion  is  effected  at  constant  pressure  and  at 
constant  temperature,  the  difference  of  the  heat-content  in  the 
original  and  final  state  is  calculated  as  follows : 

Heat  content  =  spec,  heat  X  abs.  temperature 

Original  system  =  1.5  (6.5  +  0.0006  T)  T 

Final  system  =  (6.5  +  0.0029  T)  T 

Decrease  of  heat  content  =  3.257  T  -  0.002  T2 

If  we  deduct  this  decrease  of  the  heat  content  (A  W)  from 
the  energy  of  reaction,  we  get 

QT  -  A  W  =  58,294.6  cal. 

We  have  to  consider  now  the  change  of  the  volume-energy. 
The  combustion  taking  place  at  constant  pressure,  the  volume 
is  decreased  in  the  ratio  1.5  to  1,  i.e.,  1  mol  steam  is  formed  from 
1.5  mols  hydrogen  and  oxygen.  The  volume-energy  of  the  sys- 
tem is  hereby  increased  by  0.5  RT.  This  increase  of  the 
volume-energy,  however,  takes  place  under  the  influence  of  the 
outside  pressure,  is  therefore  representing  the  addition  (supply) 
of  foreign  energy,  and  therefore  has  not  to  be  considered  here. 

Hence  we  have,  for  the  decrease  of  the  chemical  energy  of 


26  HEAT   EX  ERG  Y   AXD   FUELS 

the  system  in  the  complete  transformation  from  original  to  the 
final  state, 


We  get  the  same  result  if  the  reaction  takes  place  at  constant 
volume.  In  this  case  both  the  energy  of  reaction  and  the 
decrease  of  the  heat-content  become  less  by  \  RT,  since  cv  is 
used  instead  of  cp. 

The  change  of  the  chemical  energy  is  therefore  independent 
of  the  temperature  and  equal  to  the  energy  of  reaction  at 
absolute  zero. 

TABLE  I. 

ENERGY    OF    VARIOUS    REACTIONS. 


g.-molecules. 

K.-cal. 

H2  +  £  O2  —  >  H2O 

58294  6 

CO  +  }  O2  —  >  CO2  
C  +  £  O2  —  »  CO  
C  +  O2  ->  C02  
N2  +  O2  ->  2  NO  
2  CO  —  >  CO2  +  C  

68182.4 
28674.5 
96856.9 
43000.0 
39507.9 

CO2  +  H2  —  >•  CO  +  H2O 

-   9887  8 

C  +  H,O  —  >  CO  +  H2 

—  29620  1 

C  +  2  H2O  -»  CO2  +  2  H2  

-19732.3 

As  the  direction  of  chemical  reactions  is  not  independent  of 
the  temperature,  the  chemical  changes  of  state  do  not  neces- 
sarily depend  upon  the  chemical  energy  alone,  but  also  upon 
other  forms  of  energy.  When  considering  a  measure  of  chem- 
ical affinity  the  chemical  energy  alone  is  not  sufficient,  and  we 
have  to  use,  therefore,  the  change  of  the  free  energy  of  the 
system,  in  which  the  quantity  q0  appears  as  independent  of  the 
temperature  (chemical  energy). 

We  have  seen  above  that  chemical  equilibrium  can  only  take 
place  if  the  intensity  of  the  chemical  energy  before  the  change 
equals  the  intensity  after  the  change.  Otherwise  such  a  change 
of  state  should  take  place  that  the  intensity  of  this  energy  in 
the  system  decreases.  If,  notwithstanding,  this  transformation 
does  not  occur,  the  reason  for  this  can  only  be  looked  for  in  the 
compensating  effect  of  other  forms  of  energy.  This  is  of  the 


FORMS  OF  ENERGY  .  27 

greatest  importance,  as  is  shown  by  Ostwald  in  the  following 
explanation : 

"In  chemical  energy  the  possibility  of  compensating  differ- 
ences of  intensity  is  apparently  very  general,  as  can  be  seen 
from  the  fact,  that  in  many  cases  it  can  be  preserved  without 
loss,  practically  speaking,  for  an  indefinite  length  of  time. 
The  possibility  of  using  chemical  energy  (i.e.,  of  transforming 
it  into  other  forms)  is  necessarily  connected  with  the  pres- 
ence of  differences  of  chemical  intensities,  which  can  be  kept 
up  (i.e.,  compensated)  as  long  as  desired. 

"The  forms  of  compensating  energy  can  only  in  rare  cases 
be  observed.  This  is  the  reason  why  we  know  so  little  about 
the  presence  of  a  function  of  chemical  intensity.  We  see  that 
in  spite  of  the  possibility  of  transformation  of  the  chemical 
energy  into  other  forms,  for  instance,  in  a  mixture  of  oxygen 
and  hydrogen,  no  such  transformation  takes  place  as  long  as 
the  temperature  remains  below  a  certain  point.  In  such 
cases  we  speak  of  a  'passive  resistance.'  We  can  explain  these 
phenomena  by  supposing  that  a  compensation  of  the  differences 
of  chemical  intensity,  by  other  forms  of  energy,  actually  takes 
place,  and  that  between  the  stage  of  oxy hydrogen-gas  and  of 
water  at  low  temperatures  intermediate  stages  are  contained, 
which  for  the  transformation  (the  other  energy-quantities 
remaining  constant)  would  at  first  effect  an  increase  of  the 
intensity  factor;  afterwards  a  very  considerable  decrease  of  the 
same,  corresponding  to  the  state  of  water,  would  take  place. 
Such  states  are  called  metastabile." 

3.  Electric  Energy.  The  magnitude  of  intensity  of  electric 
energy  is  called  electromotive  force,  or  potential  difference. 
While,  however,  the  intensity  of  heat,  the  temperature,  is 
counted  from  an  absolute  zero  point,  being  therefore  always 
positive,  no  such  point  has  been  found  for  electric  potential. 
It  is  therefore  necessary  to  use  an  arbitrary  zero-point 
whereby  positive  and  negative  potential-values  are  obtained. 

The  quantity  of  electricity  is  used  as  a  factor  of  capacity. 
If  we  denote  the  same  with  Ev  the  potential  with  n  and  the 
electrical  energy  with  Ee,  we  have 

E     E° 

Hi   =  —  y 

71 

or,  Ee  =  En. 


28  HEAT  ENERGY  AND  FUELS 

For  the  quantities  of  electricity  the  law  of  conservation  can  be 
expressed  as  follows:  The  total  quantity  of  electricity  is  con- 
stant, and  equal  quantities  of  positive  and  negative  electric 
energy  are  always  present. 

If  two  quantities  of  electricity,  +  E  and  —  E,  concentrated  in 
mathematical  points  at  a  distance  r  from  each  other,  act  upon 
each  other,  the  potential  difference  being  TT,  they  exert  upon 
each  other  a  force  /,  which  is  given  by  the  equation 

3  k'E^- 

f-  -*— 


K  depends  on  the  nature  of  the  medium  between  the  two 
electric  quantities,  and  is  called  its  dielectric  constant.  If  we 
call  the  distance  traversed  by  the  two  electric  quantities  under 
the  influence  of  this  force  dr,  we  have  for  the  electric  energy 


and  therefore  for  a  change  of  the  distance  from  r'  to  r, 


If  we  make  r'  =  &  ,  we  have 

E-E   -**£', 


r 

If  El  and  E2  are  both  positive  or  both  negative,  we  see  that 
—  is  positive,  i.e.,  the  electric  energy  increases  with  the 


decreasing  distance,  or:  the  two  electric  quantities  of  like  sign 
repel  each  other.     If,  however,  E1  is  positive  and  E2  negative, 

77"E1    ~p 

or  vice  versa,  —  -—  becomes  negative;  electric  quantities  of 
unlike  signs  attract  each  other. 


FORMS  OF  ENERGY  29 

If  we  have  two  infinitely  large  quantities  of  electricity  of 
opposite  sign  stored  in  reservoirs  having  a  potential  difference 
TT,  and  we  connect  these  two  electricity  reservoirs  by  means  of 
a  conductor,  electric  energy  will  flow  from  both  into  the  con- 
ductor in  the  same  way  that  heat-energy  passes  to  a  cold 
body.  Thereby  the  two  electric  quantities  neutralize  each 
other  in  the  conductor,  the  electric  energy  being  transformed 
into  heat.  This  shows  how  the  electric  current  is  produced. 

If  the  two  quantities  of  electricity  are  not  infinitely  large 
the  generation  of  a  uniform  electric  current  (i.e.  the  preserva- 
tion of  the  same  potential-difference  between  two  cross  sections 
of  the  conductor)  will  only  be  possible  if  the  electric  energy 
consumed  in  the  conductor  in  the  time-unit  is  constantly 
replaced  at  the  source  of  the  electric  current.  If  we  refer  this 
process  to  the  time-unit,  calling  the  ratio  of  quantity  of  elec- 
tricity to  time  -  =  ij  intensity  of  current,  this  intensity  of 

current  must  be  proportional  to  the  potential  difference  n  and 
furthermore  be  dependent  on  a  coefficient,  the  quantity  of 
which  is  determined  by  the  quality  of  the  conductor.  This 

coefficient  is  the  conductance  Z;   its  reciprocal  value  r  =  -  is 

L 

called  the  resistance  of  the  conductor. 
We  thereby  arrive  at  Ohm's  law : 

i  =  ln 

7T 

r 

We  have  seen  above  that  in  the  conductor  free  electricity  is 
neutralized,  or  electric  energy  is  converted  into  heat.  If  the 
potential  difference  across  the  ends  of  the  conductor  is  n  and  if 
no  other  energy  except  heat  is  generated,  we  will  have,  if  we 
call  the  heat  quantity  formed  from  electric  energy  "  W," 

W  =  Qx. 

W 

Considering  also  the  time  --  =  q, 

t 

QTT 

we  have  q  =—  . 


30  HEAT   ENERGY  AND   FUELS 

As  —    =  i  (intensity)  and  as  according  to   Ohm's    law  TT  =  rr, 

I/ 

we  can  write 

q  =  i2ry 

i.e.,  the  rate  at  which  heat  is  generated  in  a  conductor  is  pro- 
portional to  the  resistance  and  to  the  square  of  the  intensity. 
This  is  Joule's  law. 

Another  important  law  of  electrochemistry  is  Faraday's: 
All  motions  of  electricity  in  electrolytes  take  place  only  with 
simultaneous  motion  of  ions,  so  that  with  equal  quantities  of 
electricity  chemically  equivalent  quantities  of  the  various  ions 
are  moved.  This  law  is  correct  for  every  kind  of  electricity- 
movement  in  conductors  of  the  second  class. 

Of  special  interest  for  us  is  the  transformation  of  chemical 
into  electrical  energy  as  we  find  it  in  galvanic  batteries.  It 
was  thought  at  first  that  herein  the  chemical  energy  is  per- 
fectly transformed  into  electricity.  This,  however,  is  not 
correct. 

In  general  we  can  express  these  conditions  by  the  equation  : 


wherein  Ee  means  electrical  energy,  Ec  chemical  energy,  Q  the 
quantity  of  electricity  transferred  in  the  electrolyte,  -  the  poten- 
tial difference  and  T  the  absolute  temperature. 

The  radiant  energy  is  the  least  known  of  any  form  of  energy. 
Ostwald  says  in  regard  to  the  energy  of  radiation  : 

"  The  law  of  the  conservation  of  energy  shows  a  discrepancy, 
as  we  know  some  phenomena  in  which  energy  present  dis- 
appears beyond  the  power  of  our  senses  and  means  of  obser- 
vation. It  does  not,  however,  disappear  absolutely,  as  we  can 
get  back  a  quantity  of  energy  equal  to  the  amount  lost.  But 
in  all  these  cases  it  can  be  proved  that  a  certain  (generally 
very  little)  time  has  elapsed  during  which  the  energy  has  left 
one  part  of  the  system  under  observation,  but  has  not  yet 
appeared  in  the  other  part.  From  the  fact  that  the  energy 
reappears  after  a  certain  time,  we  make  the  conclusion  by 
analogy  that  it  existed  during  this  interval  in  a  different  form; 
as  long  as  it  was  present  in  this  form,  it  was  imperceptible  to 


FORMS  OF  ENERGY  31 

us  until  after  its  retransformation  into  one  of  the  forms  of 
energy  that  we  can  perceive  with  our  senses." 

This  form,  in  which  the  energy  has  no  connection  with,  and 
no  relation  to  our  senses,  is  called  radiant  energy  or  energy  of 
radiation.  By  the  regular  relation  between  the  disappearance 
of  energy  from  one  place  and  its  reappearance  at  another  place, 
we  conclude  that  energy,  if  transformed  into  radiant  form, 
travels  through  the  space  with  a  velocity  of  3  X  1010  cm.  per 
second.  This  is  called  the  velocity  of  transmission  of  light  (ray) ; 
it  is  correct,  however,  for  radiating  energy  in  general,  from 
which  light  may  originate.  Electric  energy  is  easily  changed 
into  radiant  energy,  which  travels  at  the  same  speed,  as  energy 
originated  from  heat  and  chemical  energy,  which  is  generally 
called  light.  Based  upon  W.  Weber's  work  Maxwell  found,  by 
comparing  the  formula  for  the  electro-dynamic  effect  (long 
distance)  and  for  the  motion  of  light,  that  the  principal  con- 
stants 4are  identical,  and  Hertz  lately  demonstrated  by  means 
of  experiments  that  the  periodical  motions  of  radiant  energy, 
through  space,  generated  by  rapid  electric  oscillations,  are 
governed  by  the  same  law  as  the  optical  motions.  To  infer, 
therefore,  as  is  done  generally  at  present,  that  light  is  an 
electromagnetic  phenomenon,  is  as  incorrect  as  if  one  should 
conclude,  from  the  fact  that  burning  phosphorus  emits  light, 
that  the  light  is  a  chemical  phenomenon.  We  have,  in  all 
these  cases,  transformations  of  other  forms  of  energy  into 
radiant  energy,  that  follow  their  own  laws  and  can  be  recon- 
verted by  proper  means  into  every  other  form  of  energy. 

Radiant  energy  can,  as  the  other  forms  of  energy,  be  pro- 
duced from  other  forms  of  energy  or  changed  into  the  same. 
Its  relation  to  mechanical  energy  is  the  least  known.  It  cannot 
be  said  with  certainty  at  present  whether  direct  change  of  the 
latter  into  radiant  energy  takes  place  at  all.  I  was  not  able  to 
find  a  single  positive  proof  of  this  transformation.  This  is  the 
cause  of  the  fact  that  the  mechanical  energy,  which  acts  in  the 
movement  of  the  stellar  bodies,  remains  essentially  unchanged, 
while  the  other  formations  which  contain  other  kinds  of  energy, 
that  are  more  easily  transformed  into  radiation,  do  not  show 
such  a  constancy.  The  transformation  from  radiant  into  me- 
chanical energy  has  also  not  been  proved  beyond  doubt ;  possibly 
such  a  transformation  takes  place  in  Crooke's  radiometer. 


32  HEAT  ENERGY  AND  FUELS 

Theoretically  we  should  expect  in  every  substance  that  yields 
radiant  energy,  a  mechanical  counter  effect  in  the  form  of  a  pres- 
sure which  works  contrary  to  the  direction  of  the  radiation. 

On  the  other  hand  a  pressure  in  the  direction  of  the  radiation 
corresponds  to  every  absorption  of  radiant  energy.  This  pres- 
sure is  equal  to  the  radiant  energy  contained  in  unit  volume. 
At  the  very  great  velocity  of  the  radiation  this  amount  is  gen- 
erally very  small. 

Contrary  to  mechanical  energy  thermic  energy  is  very  easily 
transformed  into  radiation.  This  change  is  so  frequent  and 
so  regular  that  the  thermic  energy  is  often  called  u  radiating 
heat.7'  This  name  is  as  misleading  as  the  definition  of  heat  as 
a  kind  of  motion;  for  the  heat  after  transformation  into  radiant 
energy  is  not  heat,  just  the  same  as  mechanical  energy,  after 
transformation  into  heat,  has  ceased  to  exist  as  mechanical 
energy;  in  the  new  state  the  energy  follows  new  laws  and 
cannot  be  called  by  the  old  name.  * 

The  change  of  heat  into  radiant  energy  cannot  be  followed 
up  in  an  absolute  manner,  since  we  have  no  means  of  measuring 
the  radiant  energy  itself,  being  forced  to  convert  the  same  into 
another  form  of  energy;  we  have  to  reconvert  it  in  this  case 
into  heat  by  placing  in  front  of  the  radiant  bodies,  bodies 
absorbing  the  rays  and  transforming  them  into  measurable 
heat.  In  other  words  the  receiver  has  to  be  as  sensitive  a 
thermometer  as  possible.  The  receiver  has  to  contain  a  certain 
heat  of  certain  temperature,  and  must  therefore  also  radiate, 
and  the  heat-quantity,  which  is  perceptible  on  account  of  the 
absorbed  radiation,  is  the  difference  between  the  latter  and  the 
emitted  heat. 


VOLUME   I. 

THE  CHEMICAL  TECHNOLOGY  OF  HEAT 
AND  FUELS. 


VOLUME  I. 

THE  CHEMICAL  TECHNOLOGY  OF  HEAT  AND  FUELS. 

THE  chemical  technology  of  heat  treats  of  the  methods  used 
in  the  industries  for  the  transformation  of  chemical  energy  into 
heat. 

This  transformation  generally  takes  place  by  means  of  a 
chemical  process  called  combustion,  which  in  all  commercial 
processes  used  up  to  the  present  time  consists  of  oxidation. 
The  oxygen  required  is  taken  either  from  the  atmosphere  or  from 
oxides,  the  latter  being  thereby  reduced.  Lately  experiments 
that  look  very  promising  have  been  made  to  produce  pure 
oxygen  on  a  large  scale  or  to  increase  the  oxygen  content  of  the 
air  for  obtaining  an  increased  effect  in  the  combustion. 

The  materials  which  are  used  commercially  for  generating 
heat  are  called  fuels.  They  are  either  used  as  they  occur  in 
nature  (natural  fuels)  or  are  made  to  undergo  certain  changes 
before  being  used  (artificial  fuels). 

The  object  of  combustion,  as  above  stated,  is  the  trans- 
formation of  chemical  energy  into  heat.  It  will  therefore  be 
necessary  to  become  acquainted  with  the  methods  of  measur- 
ing the  generated  heat  and  also  with  the  methods  that  enable 
us  to  determine  the  energy-content  of  the  fuels. 

Primarily,  we  are  concerned  with  the  measurement  of  the 
intensity  factors  of  heat  energy,  i.e.  the  temperature,  since  the 
capacity-factors  (the  specific  heats)  are  generally  known,  and 
hence  do  not  have  to  be  determined  in  every  case. 

Second  in  order  comes  the  experimental  determination  of  the 
calorific  value.  These  determinations  are  of  two  kinds,  depend- 
ing on  whether  the  quantity  of  heat  yielded  by  the  combustion 
of  a  certain  quantity  of  fuel  is  to  be  determined,  or  whether 
the  highest  temperature  that  can  be  reached  theoretically  by 
combustion,  is  to  be  ascertained. 

Finally  it  will  be  necessary  to  study  in  detail  the  process  of 
combustion. 

35 


36  HEAT   ENERGY  AND  FUELS 

All  these  points  are  considered  in  Part  I  of  this  work.  Part 
II  contains  the  science  of  firing,  i.e.  all  the  processes  that  favor 
the  utilization  of  the  combustion  heat,  or  reduce  the  unavoid- 
able heat  losses,  and  also  the  discussion  of  the  different  methods 
of  industrial  firing. 

Part  III  is  added  as  an  appendix,  treating  of  the  various 
chemical  methods  of  heat  abstraction  (refrigeration). 


PAET   I. 

HEAT   MEASUREMENT,  COMBUSTION 
AND    FUELS. 


CHAPTER   I. 

THE   MEASUREMENT    OF   HIGH   TEMPERATURES 
(PYROMETRY). 

THE  measurement  of  temperature  is  of  the  utmost  importance 
in  the  industries,  because  on  the  one  hand  certain  processes  and 
reactions  take  place  only  within  certain  limits  of  temperature, 
and  on  the  other  hand  an  increase  of  temperature  above  a 
certain  value  means  an  increase  of  heat  loss  and  a  waste  of  fuel. 
Instruments  for  measuring  temperature  are  generally  called 
thermometers;  thermometers  used  for  measuring  high  temper- 
atures, however,  are  called  pyrometers.  Widely  different  prop- 
erties of  certain  substances  which  vary  with  temperature 
have  been  used  or  proposed  for  the  measurement  of  tempera- 
ture: Change  of  length  and  volume  of  various  substances, 
variation  in  the  pressure  of  gases  and  vapors,  melting  points  of 
different  substances,  heat  given  up  by  hot  substances  in  cool- 
ing, color  of  emitted  light,  change  of  electric  resistance  and 
thermoelectric  behavior,  heat-conductivity,  etc. 

We  are  going  to  describe  below  the  most  important  instru- 
ments of  this  kind : 

1.  Ordinary  thermometers,  in  which  the  apparent  expansion 
of  a  liquid  (generally  mercury,  at  low  temperatures,  alcohol)  in 
a  containing  glass  vessel,  is  measured.  Since  the  ordinary 
thermometers  can  be  used  only  up  to  the  vicinity  of  the  boiling 
point  of  mercury  (358°  C.  at  atmospheric  pressure),  tempera- 
tures up  to  about  500°  C.  require  instruments  that  contain  a 
quantity  of  hydrogen  or  nitrogen  above  the  mercury,  instead  of 
a  vacuum.  When  used  they  have  to  be  heated  up  slowly,  i.e. 
gradually  inserted  into  the  medium  or  space,  the  temperature 
of  which  is  to  be  measured. 

37 

•/*&'  3*^ 

f  OF  THE     " 

f    UNIVERSITY  i 


38 


HEAT   ENERGY  AND   FUELS 


For  exact  measurements  of  temperature  the  following  errors 
have  to  be  considered : 

1.  Reading  error. 

2.  Graduation  error. 

3.  Error  due  to  pressure  (inside  or  outside). 

4.  Error  due  to  meniscus. 

5.  Erroneous  determination  of  the  fixed  points. 

6.  Error  due  to  time  lag  of  thermometer. 

7.  Error  due  to  glass-expansion. 

We  want  to  consider,  in  a  few  words,  the  most  important  of 
these  sources  of  error. 

To  obtain  correct  readings  the  visual  ray  has  to  be  perpen- 
dicular to  the  graduation. 

For  exact  measurements  of  temperature  it  is  a  disagreeable 
fact  that  thermometers,  after  some  time,  show  incorrect  read- 
ings, the  freezing  point  being  apparently  moved  upwards, 
and  returning  to  the  original  position  only  after  being  heated 
to  high  temperatures  for  several  months.  This  phenomenon  is 
called  depression.  This  depression  is  in  close  relation  to  the 
composition  of  the  glass : 

TABLE   II. 
DEPRESSION    FOR    VARIOUS    COMPOSITIONS    OF    GLASS. 


Depres- 
sion. 

SiO2 

A12O3 

CaO 

MgO 

PbO 

K,O 

Na2O 

Degree 
0. 
0.08 
0.09 
0  09 

50.83 
72.04 
65.42 
69.04 

1.04 
2.42 
0.93 
0.89 

0.52 
8.20 
13.67 
12.21 

27.98 

11.08 
1.63 
19.46 
18  52 

15.32 

0.10 

56.74 

0.66 

0.18 

29.86 

12.48 

0  11 

65  00 

2  04 

13  58 

19  51 

0  07 

0.12 
0.15 
0.20 
0.24 

72.09 
69.52 
64.48 
70.29 

1.45 
3.86 
1.48 
2.29 

11.20 
9.13 
5.68 
9.55 

0.12 
0.71 

12.71 

1.88 
3.07 
3.55 
14.51 

13.41 
13.77 
12.81 
2  48 

0  31 

75  65 

1  34 

6  11 

5  68 

11  50 

0  35 

74  72 

1  35 

9  10 

5  86 

9  03 

0.36 
0.37 
0.40 
0.40 
0.48 
0  61 

66.42 
66.55 
63.47 
60.56 
68.30 
70.29 

3.35 
1.31 
1.77 
1.14 
1.28 
2.49 

10.70 
13.37 
10.10 
10.21 
10.41 
8.68 

0  30 

14.55 
15.50 
12.24 
3.52 

8.27 
12  06 

4.57 
3.07 
11.95 
24.45 
12.08 
5  38 

0.66 

72.44 

1.60 

9.23 

11.29 

6.00 

THE  MEASUREMENT  OF  HIGH   TEMPERATURES 


39 


TABLE   III. 
DEPRESSION   FOUND  BY  WIEBE. 


Depres- 
sion. 

Si02 

Fe203 

A1303 

CaO 

MgO 

Mn2O3 

As,03 

K2O 

Na2O 

_ 

0.04 
0.15 

64.45 
64.66 

0 
0.53 

.81 
0.24 

12.36 
13.38 

0.22 
0.27 

Trace 
Trace 

PhO 

0.89 
0.87 

20.09 
18.89 

0.86 
1.48 

0.15 

0.38 
0.38 
0.40 
0.44 
0.65 
0  07 

49.49 

64.49 
68.62 
69.58 
66.53 
66.74 
70  0 

0 

0.61 
0.53 
0.46 
0.43 
0.30 

.35 

0.42 
2.37 
2.09 
2.18 
0.21 

1.20 

11.56 
7.36 
7.90 
9.44 
8.68 
16.5 

0.67 

0.38 
0.36 
0.30 
0.21 
0.22 

33.90 
Mn9O3 
0."77 
0.34 
Trace 
Trace 
0.08 

0.35 
Trace 
0.27 
0.74 

12.26 

17.14 
3.56 
3.97 
3.95 
10.57 
13  5 

1.54 

3.75 
16.89 
15.35 
16.15 
12.72 

0  07 

70  0 

15.0 

15  0 

1  05 

66  0 

6  0 

14  0 

14  0 

Other  tests  made  by  Abbe  and  Schott  also  proved  that  lead- 
potassium  glass,  potassium-lime  glass  or  sodium-lime  glass  show 
the  lowest  depression,  which,  however,  increases  if  potassium 
and  sodium  are  present  in  a  glass  simultaneously. 

According  to  these  observations  a  standard-thermometer 
glass  of  the  following  composition  is  manufactured  by  Schott  & 
Genossen  in  Jena : 

Silicic  acid  67  per  cent 

Boracic  acid 2  per  cent 

Alumina 2.5  per  cent 

Lime 7  per  cent 

Oxide  of  zinc   7  per  cent 

Soda  (caustic) 14.5  per  cent 

This  glass,  after  previously  being  heated  to  100°  C.  shows  a 
transient  fall  of  the  zero-mark  of  only  0.05  to  0.06°  C. 

The  correction  of  the  thermometer-reading  on  account  of  the 
meniscus  is  made  by  means  of  the  equation  :* 

T  =  t  +  0.000148  n(t  -  t'), 

wherein     T  means  corrected  temperature. 
t  means  observed  temperature. 
if  means  average  temperature  of  the  meniscus. 
n  means    length   of   the   meniscus   in   thermometer- 
degrees. 
*  (See  also  the  following  table  of  Thorpe.) 


40 


HEAT  ENERGY  AND  FUELS 


3    8 

PQ     a 
B 


C<l  C^l  (M  <N  <M  (N  C<» 


0000000 
<*»o<ot^oooso 


THE  MEASUREMENT  OF  HIGH  TEMPERATURES 


41 


0.000148  is  an  empirical  coefficient  that  approaches  the 
apparent  expansion-coefficient  of  mercury  in  glass  (0.000154). 

2.  Graphite  pyrometer  and  metal  pyrometer.  Notwithstand- 
ing their  defects  these  instruments  are  widely  used.  They  are 
based  upon  the  unequal  expansion  of  two  different  solid  sub- 
stances, and  they  measure  the  difference  of  expansion  of  two 
different  solid  substances. 

Especially  the  graphite  pyrometer  is  largely  used.  However, 
it  is  not  at  all  reliable,  as  is  shown  by  the  following  table,  in 
which  t  means  the  reading  from  the  pyrometer  and  T  the  tem- 
perature determined  by  the  Weinhold  calorimeter: 

TABLE  V. 

COMPARISON    OF   GRAPHIC   PYROMETER  WITH    THE  WEINHOLD    CALORI- 
METER. 


t 

T 

t 

T 

t 

T 

t 

T 

604 

500 

775 

573 

869 

553 

888 

555 

650 

512 

814 

535 

873 

524 

906 

555 

736 

520 

818 

567 

874 

571 

909 

553 

756 

585 

835 

561 

875 

594 

935 

575 

Furthermore,  these  pyrometers  do  not  go  back  entirely  to 
air-temperature  after  cooling,  but  show  a  temperature  20°- 
60°  higher,  which  defect  increases  continuously,  so  that  three 
graphite  pyrometers  (examined  by  Beckert)  that  were  only 
exposed  to  hot  blasts  of  less  than  500°  C.  within  two  months 
showed  over  800°,  and  went  to  about  200°  above  the  zero-mark. 

Metal  pyrometers  show  similar  faults.  With  three  of  these 
pyrometers  Weinhold  obtained  the  following  rccorrections  as 
compared  with  air-pyrometers.  (Table  VI.) 

A  peculiar  instrument  of  this  kind  is  Joly's  meldometer, 
which  is  used  for  determining  melting  points. 

3.  Wedgewood's  pyrometer  is  based  upon  the  contraction  of 
a  clay  cylinder,  which,  after  being  heated  to  the  temperature 
to  be  measured,  is  allowed  to  cool  to  ordinary  temperature; 
then  the  decrease  of  volume  of  the  clay  resulting  from  its  change 
at  high  temperature  is  measured;  one  degree  corresponds  to  a 
contraction  of  ^VTT  of  the  original  dimension.  The  zero-point  of 


42 


HEAT  ENERGY  AND  FUELS 


the  pyrometer  corresponds  to  a  temperature  at  which  complete 
dehydration  of  the  clay  takes  place,  i.e.  about  600°  C.  The 
contraction  of  the  clay  cylinder  is  measured  by  locating  same 
between  two  graduated  lines,  which  form  a  certain  angle. 
(Fig.  1.) 

TABLE   VI. 

COMPARISON    OF    VARIOUS    METAL    PYROMETERS   WITH    AN    AIR 
PYROMETER.      (WEINHOLD.) 

(a)  Gauntlett's  Pyrometer  (Iron  and  Brass). 


I 

First  Series  of  Tests. 

After  Continued  Use. 

Air  Pyrometer. 

Gauntlett  Pyrometer. 

Air  Pyrometer. 

Gauntlett  Pyrometer. 

Degrees 

Degrees 

Degrees 

Degrees 

507 

325    ' 

407 

310 

13 

-10 

20 

10 

328 

162 

319 

200 

533 

362 

441 

308 

227 

98 

12 

8 

330 

170 

471 

345 

20 

-10 

348 

220 

12 

6 

0 

-2 

(6)    Bock's  Pyrometer  (Iron  and  Brass). 


Air  Pyrometer. 

Bock's  Pyrometer. 

Air  Pyrometer. 

Bock's  Pyrometer. 

Degrees 
305 
464 
472 
526 
636 

Degrees 
125 
245 
250 
298 
352 

Degrees 
347 
478 
565 
716 

Degrees 
225 
210 
330 
400 

(c)  Oechsle's  Spiral  Pyrometer  (Platinum-Silver). 


Air  Pyrometer. 

Oechsle's  Pyrometer. 

Air  Pyrometer. 

Oechsle's  Pyrometer. 

Degrees 

Degrees 

Degrees 

Degrees 

277 

325 

257 

275 

272 

315 

15 

-   7 

273 

310 

316 

336 

311 

338 

362 

381 

352 

372 

494 

475 

404 

401 

0 

-52 

THE  MEASUREMENT  OF  HIGH   TEMPERATURES         43 


These  pyrometers  are  seldom  used  to-day,  as  they  give  widely 
varying  results  even  with  slight  variations  in  their  composition 
and  method  of  manufacture;  furthermore  their  results  are  not 
proportional  to'  the  ones  of  the  air  pyrometer, 
which  at  present  is  taken  as  standard  ther- 
mometer. 

LeChatelier  found,  for  instance  : 

Air  pyrometer  °  C. 

900     1000     1100     1200     1300     1400 
Wedgewood's  pyrometer 

20        30        70      130      152      160 

In  ceramic  factories,  however,  where  not 
an  actual  temperature-measurement  has  to 
be  made,  but  only  a  certain  temperature 
has  to  be  maintained,  Wedgewood's  pyrom-  FlG-  l~ 
eter  can  be  advantageously  used.  In  France 
circular  cakes  5  cm.  thick,  having  a  diameter  of  5  cm.,  are 
used  for  this  purpose,  being  pressed  out  of  the  clay-mass 
without  moistening  and  then  burned. 

4.  Gas  or  air  thermometers  are  based  upon  Boyle-Gay- 
Lussac's  law,  and  are  considered  as  standard  instruments, 
with  which  all  others  are  compared.  They  are  used  either 
with  constant  volume  or  constant  pressure  . 

For  a  permanent  gas,  which  at  the  absolute  temperature  T 
and  the  pressure  P,  occupies  the  volume  V,  we  have  the  law 

PV  =  nRT 

(wherein  n  stands  for  the  number  of  mols  of  gas  in  volume  V). 
If  we  change  the  temperature  of  this  gas  to  Tv  while  keeping  its 
volume  constant,  the  pressure  is  changed  to  Px,  and  we  have 


or 


or 


•i'4  HEAT   ENERGY  AND  FUELS 

By  this  method  we  can  measure  a  change  of  temperature  by 
the  corresponding  change  of  the  pressure. 

If,  however,  we  change  the  temperature  of  the  gas  from  T 
to  Tv  keeping  the  pressure  P  constant,  the  volume  of  the  gas  is 
changed  to  Vv  and  we  have 

PV1  =  nRTv 
or 

T      V 

J  i  _  v  i 

T  "  V 
or 

T^-T      V1  -  V 


We  measure  here  the  change  of  temperature  by  the  change 
of  volume. 

As  the  active  medium  a  permanent  gas  is  used  (nitrogen, 
hydrogen,  or  air),  which  is  enclosed  in  a  vessel  of  practically 
unchangeable  volume.  The  Celsius-graduation  is  used,  the  freez- 
ing point  serving  as  zero-mark. 

Temperatures  between  0  degree  and  100  degrees  are  gener- 
ally measured  with  a  thermometer  of  constant  volume.  Above 
100°  C.  however,  the  pressure  increases  so  rapidly  that  the 
strength  of  the  pyrometer  may  be  exceeded.  Therefore  for 
such  temperatures  instruments  with  constant  pressure  are 
used.  If  the  pressure  is  measured  in  atmospheres  we  have  for 
the  first  method 

t  =  (P  -  1)  273, 
and  for  the  second  method  : 


Up  to  500°  C.  the  thermometer-  vessel  can  be  made  of  glass, 
but  for  higher  temperatures  glass  softens.  Platinum  vessels 
were  first  tried  for  temperatures  higher  than  500°  C.,  but  not 
successfully,  since  hydrogen  (which  is  generally  used)  per- 
meates platinum  at  high  temperatures.  Porcelain  vessels,  if 
made  impermeable  for  gas  by  glazing,  can  be  used  safely  up  to 
1000°  and  even  higher. 


THE  MEASUREMENT  OF  HIGH   TEMPERATURES          45 

For  avoiding  the  error  due  to  the  change  of  the  quantity  of 
the  enclosed  gas  on  account  of  the  permeability  of  the  vessel, 
a  method  invented  by  Becquerel  can  be  used.  It  consists  of 
forcing  a  further  quantity  of  gas  into  the  volume  V  of  the  pyro- 
meter containing  gas  of  the  temperature  (to  be  measured)  T 
and  of  pressure  P  and  measuring  the  pressure  required  for  this 
purpose.  Immediately  before  adding  this  quantity  of  gas  we 
have  in  the  apparatus  n  mols  of  gas  of  volume  Vf  pressure  P  and 
temperature  (to  be  measured)  T, 

PV  =  nRT. 

We  now  add  the  gas-volume  v  measured  at  t  and  p,  for  which  we 
have 

pv  =  n'Rt. 

After  pressing  this  gas-quantity  in  we  have  in  the  constant 
volume  V  of  the  apparatus,  gas  of  the  temperature  (to  be 
measured)  T  and  of  pressure  P' : 

P'V  =  (n  +  n')  RT, 
and  therefore 

PV      jyv  _  P^V 
T      '   t  '    ~T 

In  this  equation  T  is  the  only  unknown  quantity.     We  have 

T__(Pf  -  P)V 

~i~  pv 

or 

T  =  (P'  -  P)V  t 
pv 

The  applicability  of  this  method  is  based  upon  the  fact  that 
less  than  a  minute  is  required  for  measuring  and  introducing 
the  additional  quantity  of  gas  so  that  the  error  caused  by  the 
permeability  of  the  vessel  during  this  short  period  is  very 
small  and  negligible. 

The  only  defect  of  this  apparatus  is  the  uncertainty  of  our 
knowledge  (exactly)  of  the  expansion  of  the  pyrometer-vessel 
at  high  temperatures.  An  instrument  of  this  kind,  very  con- 
venient for  practice,  which,  however,  has  to  be  handled  care- 
fully on  account  of  the  fragility  of  the  porcelain  vessel,  was 


46 


HEAT    ENERGY  AND   FUELS 


constructed  by  T.  Wiborgh.  Figs.  2  and  3  show  same  in  the 
older  construction.  The  thermometer-bulb  V,  having  a  con- 
tent of  about  12  cm.,  is  prolonged  into  a  porcelain  tube  of 
20  mm.  outside  and  0.5  mm.  inside  diameter.  This  tube, 
which  is  practically  a  capillary  tube,  and  can  be  set  upon  the 
other  parts  of  the  instrument,  has  to  be  very  strong,  and  is 


FIGS.  2  and  3.  —  Wiborgh  Pyrometer. 

built  with  heavy  walls.  The  tube  is  cemented  into  the  metal 
shell  A,  which  can  be  screwed  upon  the  metal  cylinder  H', 
whereby  a  connection  is  made  between  the  tube  and  the  mano- 
meter EVE'. 

The  glass  tube  (manometer)  is  somewhat  larger  (1.5  to  2 
mm.)  at  m  for  a  length  of  10  mm.;  then  comes  another  enlarge- 
ment containing  the  air  volume  V  that  is  to  be  pressed  in  the 
thermometer-bulb  when  determining  the  temperature.  At  mf 
the  tube  E  opens  into  the  longer  manometer-tube  Bv  which  is 


THE  MEASUREMENT  OF  HIGH   TEMPERATURES          47 

about  2  mm.  inside  and  8  mm.  outside  diameter.  The  latter 
is  prolonged  downward  and  connects  through  a  bend  with  the 
iron  vessel  K,  which  is  filled  with  mercury.  A  cover  is  screwed 
upon  this  vessel,  the  cover  carrying  a  nut  for  the  screw  S,  by 
means  of  which  a  second  iron  cover  can  be  pressed  directly 
upon  the  mercury. 

The  screw  S  is  turned  by  means  of  the  metal  disk  $',  which 
sets  loosely  upon  the  pivotal  end  of  the  screw  so  that  the  disk 
can  easily  be  taken  off.  This  is  to  prevent  the  mercury  from 
being  forced  through  the  manometer-tube  B  into  the  ther- 
mometer-bulb by  careless  manipulation,  which  would  injure 
the  instrument.  As  further  protection  against  such  an  acci- 
dent the  tube  B  is  provided  with  another  very  small  enlarge- 
ment right  above  m,  that  is  filled  with  asbestos  to  prevent  a 
rise  of  the  mercury  beyond  this  point. 

For  protection  the  manometer-tube  is  enclosed  in  a  little 
rectangular  metal  box  D,  closed  in  front  by  a  glass  plate  G. 
The  longer  manometer-tube  Bf  projects  upward  through  the 
box  along  the  metal  tube  P.  The  metal  tube  P  contains  a 
wooden  cylinder  0,  which  can  be  turned  by  knob  0'.  The 
scale  is  fastened  to  this  cylinder,  and  is  observed  through  a 
slot  in  the  metal  tube  P.  By  turning  the  cylinder  the  correct 
scale,  i.e.  the  scale  corresponding  to.  the  barometric  height,  can 
be  brought  into  view.  For  preventing  dust  from  entering  the 
open  manometer-tube  B',  some  cotton  is  put  into  the  upper 
end,  above  which  a  glass  cap  may  be  suspended.  If  the  air- 
volume  V  is  at  the  same  temperature  as  the  thermometer- 
bulb  and  the  mercury  is  forced  up  to  the  mark  m,  and  rises  in 
the  manometer-tube  B'  to  a  certain  height,  it  indicates  the 
zero-mark  of  the  instrument  corresponding  to  the  barometric 
height. 

The  correct  scale  is  then  brought  into  position  by  turning  the 
scale-cylinder  until  the  scale,  whose  zero-mark  coincides  with 
the  barometric  height,  comes  into  view.  If,  however,  the  instru- 
ment is  so  placed  that  V  is  warmer  than  V',  it  is  not  possible 
to  find  the  correct  scale  by  this  method. 

For  avoiding  the  necessity  of  using  a  special  barometer  in 
this  case,  a  third  tube  Q,  terminating  with  a  bulb  Q',  is 
connected  to  the  manometer-tube  R.  When  the  mercury  is 
pressed  into  the  manometer  it  is  also  pressed  into  Q  and  rises  to 


48 


HEAT   ENERGY   AND  FUELS 


the  zero-mark  of  the  instrument,  at  a  certain  height  r,  marked 
on  the  glass.  Here  the  same  principle  is  used  as  in  the  pyro- 
meter in  general,  i.e.  a  certain  volume  of  air  is  pressed  into 
another;  if  we  have  the  same  temperature  in  the  tube  Q  and 
in  the  bulb  Q',  the  zero-point  of  the  pyrometer  can  be  deter- 
mined by  mark  r,  even  if  V  is  warmer  than  V '. 

For  protecting  the  lower  part  of  the  porcelain  tube  A,  which 
contains  the  thermometer-bulb,  from  quick  changes  of  tem- 
perature and  shocks,  it  is  packed  in  asbestos.  The  upper  part, 
however,  is  free. 

For  cementing  the  pyrometer  and  manometer-tubes  into 
their  respective  metal  shells,  a  cement  obtained  by  mixing 
finely  powdered  litharge  with  glycerin  to  a  thick  paste  is  used. 
This  cement  gets  hard  in  a  few  hours,  and  can  be  heated  up  to 
about  250  degrees  without  being  decomposed.  In  order  to 
prevent  the  obstruction  of  the  capillary  tube  during  the  cement- 
ing process,  a  metal  wire  is  passed  through  both  tubes;  then 
the  ends  of  the  tubes  are  partially  withdrawn  from  the  metal 
shells  and  coated  with  cement.  About  half  an  hour  later  the 
superfluous  cement  is  removed  and  the  metal  wire  taken  out. 


FIGS.  4  and  5.  —  Spring  Manometer. 

In  order  to  render  the  instrument  less  fragile  and  to  simplify 
its  manipulation  Wiborgh  replaced  the  mercury-manometer  by 
a  spring-manometer  (Figs.  4  and  5).  The  instrument  rests  in  a 
round  metal  box  with  heavy  bottom  (a),  to  which  the  por- 
celain pyrometer-tube  (rV)  is  screwed,  the  same  as  in  the  other 
instruments.  In  the  interior  of  the  box  is  a  lenticular  shaped 
metal  vessel  V,  which  can  be  pressed  together,  and  will  regain 
its  original  shape  when  the  pressure  is  released. 


THE  MEASUREMENT  OF  HIGH   TEMPERATURES         49 

Facing  plate  a  is  a  metal  plate  &,  held  in  position  by  a 
cylindrical  bearing;  it  is  provided  with  a  capillary  tube.  As  the 
lenticular  shaped  vessel  contains  openings  corresponding  to  the 
two  capillary  tubes,  V  and  V  are  brought  into  communication 
with  each  other  and  with  the  outer  air. 

A  metal  support,  fastened  to  the  box,  carries  a  shaft  e, 
which  serves  to  compress  the  vessel  V±  through  a  short  lever- 
arm  K,  which  is  connected  to  the  rod  s.  By  turning  the  shaft 
the  opening  in  the  capillary  tube  is  closed  and  the  plate  b 
pressed  against  the  lenticular  vessel  V,  compressing  the  air 
and  forcing  it  into  the  bulb  V  of  the  pyrometer. 

The  capillary  tube  in  the  hub  d  is  connected  with  the 
manometer-spring  by  means  of  a  fine  lead  tube  m.  By  means 
of  geared  wheels  the  spring  transmits  to  a  pointer  the  motion 
caused  by  the  increased  pressure. 

The  shaft  e  is  turned  by  means  of  a  forked  lever-arm  pro- 
vided with  a  knob  L. 

If  no  measurement  of  temperature  is  being  made  the  air- 
volumes  V  and  V  are  in  communication  with  the  atmosphere, 
and  the  rod  s  does  not  close  the  capillary  tube.  A  spiral 
spring  (not  shown  in  the  figure)  is  arranged  to  hold  the  lever 
in  the  position  shown  in  Fig.  4. 

The  temperature-scale  of  the  instrument  is  arranged  for  air- 
temperature  of  0°  C.  If  the  latter  is  £°,  the  air-volume  to  be 
pressed  into  the  pyrometer-bulb  is  simply  increased  to 
(1  +  at)  V,  whereby  the  same  value  is  obtained  as  if  t  were 
0°  C.  A  change  of  the  barometic  height  H  has  the  opposite 
effect,  so  that  V  has  to  be  decreased  as  the  barometric  pressure 
increases  if  the  scale  is  to  give  correct  readings.  Temperature 
and  barometric  height,  according  to  the  law  of  Boyle-Gay- 
Lussac,  bear  a  certain  fixed  ratio  to  each  other,  so  that,  for 
instance,  to  compensate  for  an  increase  of  the  barometic  height 
of  78  mm.,  the  volume  V  has  to  decrease  as  much  as  though  the 
temperature  had  fallen  30  degrees.  Therefore  one  single  scale 
can  be  used  for  reducing  the  volume  V. 

To  accomplish  this  result  the  bearing  d  is  provided  with 
a  movable  collar  g,  one  end  of  which  presses  against  a  pro- 
jection of  /,  while  the  opposite  end  is  helical  in  form,  and  fits  a 
corresponding  helix  on  the  pivot  plate  b.  By  turning  the 
cover  of  the  instrument,  which  is  connected  with  the  ring  by 


50  HEAT   ENERGY  AND   FUELS 

the  rods  n  and  0,  the  collar  g  is  raised  or  lowered,  whereby  a 
change  of  volume  of  the  vessel  V  is  effected. 

In  addition  to  the  scale  of  temperature  (0°  to  1400°  C.),  the  dial 
of  the  instrument  is  provided  with  a  small  aneroid  barometer 
Q,  a  thermometer  P,  a  scale  (from  690  to  790  mm.)  for  correct- 
ing the  barometric  pressure,  and  a  temperature  correction 
scale  attached  to  a  ring  E.  Correction  for  temperature  and 
barometric  pressure  (i.e.  setting  the  instrument  to  the  air- 
temperature  and  pressure),  ,is  made  by  reading  the  thermom- 
eter P  and  the  barometer  Q,  then  turning  the  ring  E  so  that 
the  temperature  and  barometic  readings  on  both  scales  coincide. 

If  a  measurement  of  temperature  is  to  be  made,  first  of  all 
the  ring  E  is  turned  into  the  right  position,  i.e.  the  instrument 
is  set  to  correspond  with  the  air  temperature  and  barometric 
height.  Then  the  lever  C  is  drawn  forward  as  far  as  possi- 
ble, until  the  pointer  Z  stops  moving  and  stands  still.  Then 
the  rod  s  is  pressed  down,  the  opening  of  the  capillary  tube 
closed  and  the  hub  d  pressed  down  with  the  metallic  disk; 
the  vessel  V  is  compressed  so  that  the  air  is  pressed  into  the 
pyrometer-bulb  V.  The  air-pressure  so  obtained  is  trans- 
mitted through  the  lead-tube  m  to  the  manometer-spring. 
The  latter  then  changes  its  position  and  sets  the  hand  Z  in 
motion. 

After  reading  the  temperature  the  lever  G  is  released. 
It  jumps  back,  partly  on  account  of  the  elasticity  of  the  vessel 
V,  partly  because  of  the  spiral  spring  that  is  fastened  to  the 
shaft  e;  and  the  pointer  goes  to  the  zero-mark.  This  meas- 
urement can  be  performed  in  a  few  seconds. 

The  lever-arm  G  (which  is  forked  and  elastic)  can  easily  be 
taken  off  the  shaft  and  removed,  thus  preventing  the  use  of  the 
instrument  by  unskilled  persons. 

In  order  to  render  the  porcelain  tube  less  fragile,  and  to  be 
able  to  expose  the  tube  directly  to  high  temperatures  without 
danger  of  cracking  and  breaking,  it  is  covered  with  asbestos 
and  packed  into  a  sheet-iron  tube,  the  latter  being  coated  with 
fire-clay,  quartz  and'unburned  clay. 

Both  constructions  of  Wiborgh's  air-pyrometer  can  be  bought 
from  Dr.  Geissler's  successor  in  Bonn. 

Of  the  other  practical  air-pyrometers  we  may  mention  the 
pyrometer  of  K.  V.  Karlander  (can  be  bought  from  Otto  Meyer- 


THE  MEASUREMENT  OF  HIGH   TEMPERATURES 


51 


son  in  Stockholm)  and  of  A.  Sieger  and  Walter  Duerr  (can 
be  bought  from  Alphonse  Custodis  in  Diisseldorf). 

The  air-thermometer  is  not  only  used  in  practice,  but  also 
to  a  great  extent  as  a  standard  for  calibrating  other 
instruments.  For  this  purpose  a  number  of  very  exact 
temperature-determinations  were  made  with  the  air-thermom- 
eter, a  number  of  which  are  given  in  Table  VII : 


TABLE  VII. 

ACCURATELY    DETERMINED  BOILING    AND    MELTING    POINTS. 


Substance. 

Boiling  Point. 

Substance. 

Boiling  Point. 

Naphthalin  
Mercury 

Deg.  Cent. 
218 
357 

Sulphur  (Regnault) 
Zinc 

Deg.  Cent. 
448 
921 

Sulphur 

445 

Substance. 

Melting  Point. 

Substance. 

Melting  Point. 

Cadmium  
Lead 

Deg.  Cent. 
321.7 
326  9 

Silver  (in  air)  
Silver  (pure) 

Deg.  Cent. 
955 
961  5 

Zinc 

419  0 

Gold 

1063  5 

Antimony  
Aluminium  

630.6 
657 

Copper  (in  air)  
Copper  (pure)  

1064.9 
1084.1 

The  specific  heat  of  platinum  between  0°  and  1200°  C.  was  also 
found  by  calorimetry: 

C0'=  0.0317  +  0.000006  Z. 

t  was  determined  by  means  of  an  air-pyrometer. 

Daniel  Berthelot  has  lately  by  an  ingenious  method  elimi- 
nated the  error  caused  by  the  permeability  and  expansion  of 
the  casting,  by  determining  optically  the  density  of  the  heated 
air  at  atmospheric  pressure,  and  therefrom  calculating  the 
temperature  by  means  of  the  gas-equation.  By  this  method  he 
found 

The  melting  point  of  silver  to  be  962°  C., 
The  melting  point  of  gold  to  be  1064°  C., 

which  agrees  exactly  with  the  values  given  above. 


52 


HEAT   ENERGY  AND  FUELS 


5.  Klinghammer's  thalpotasimeter  (Fig.  6).  This  instrument, 
which  can  be  used  up  to  about  800  degrees,  measures  the  vapor 
tension  of  different  liquids.  It  consists  of  a  tube  containing 


FIG.  6.  —  Thalpotasimeter  (Klinghammer). 

the  liquid  and  a  manometer.     The  following  substances  are 
used  as  the  active  medium: 


Liquid  carbon  dioxide  
Liquid  sulphur  dioxide  
Ether  (free  of  water)  

Deg.  Cent. 
From  -   65    to 
-    10 
+   35 

+    12.5 
+  100 
+  120 

Distilled  water  
Heavy  hydrocarbons  
Mercury  

+  100 
+  216 
+  357 

+  226 
+  360 

+  780 

Mercury  is  especially  suitable,  since  its  molecules  consist  of 
single  atoms,  which  make  the  internal  work  very  simple. 

This  pyrometer  has  to  be  gradually  heated  to  the  temper- 
ature to  be  measured,  in  order  to  prevent  injury  to  the  appa- 
ratus. 


CHAPTER   II. 
PYROMETRY  (Continued). 

6.  Pyrometers  in  which  the  fusibility  of  different  substances  is 
utilized  for  measuring  temperatures.  All  these  pyrometers  have 
the  disadvantage  of  only  allowing  the  determination  of  con- 
stant or  rising  temperatures  or  of  temperature-maximums ;  but 
they  are  not  suitable  for  the  observation  of  temperature- 
changes  (up  and  down),  which  are  frequently  of  commercial 
importance. 

(a)  Princep's  alloys: 

These  are  alloys  of  gold  and  silver,  or  of  gold  and  plati- 
num, the  melting  point  of  which  was  determined  by  Erhard 
and  Schertel  by  means  of  an  air-pyrometer.  These  deter- 
minations are  shown  in  Table  VIII. 

The  error  of  these  determinations  of  the  melting  point  is 
generally  less  than  20  degrees,  but  in  most  cases  it  is  very 
much  smaller.  The  above  melting  points  were  actually 
measured  up  to  1400°  C.  by  the  air- thermometer;  the  higher 
values  were  determined  by  graphic  interpolation  by  using  the 
melting  temperature  of  platinum  as  found  by  Violle. 

An  important  requirement  for  temperature-determinations 
by  this  method  is  the  use  of  sufficiently  pure  metal  for 
Princep's  alloys.  It  is,  therefore,  of  advantage  to  prepare  them 
in  a  state  of  sufficient  purity  or  to  obtain  them  from  a  reliable 
source.  Erhard  and  Schertel  obtained  the  pure  metals  as  fol- 
lows :  The  silver  was  precipitated  from  diluted  ammoniacal  solu- 
tion by  ammonium-sulphide;  gold  was,  after  precipitation  by 
sulphate  of  iron,  transformed  into  sodium-gold-chloride  and 
from  the  solution  the  pure  crystals  precipitated  by  means  of 
oxalic  acid.  For  purifying  the  platinum,  platinum-salammoniac 
was  treated  (according  to  Glaus)  with  sulphuretted  hydrogen- 
solution,  for  reducing  iridium  to  sesquichloride.  The  sponge 
obtained  from  the  platinum-salammoniac  (free  of  iridium)  was 
melted  upon  chalk  in  an  oxy hydrogen-flame.  The  different 

63 


54 


HEAT   ENERGY   AND   FUELS 


mixtures  can  advantageously  be  prepared  by  using  wires  made 
out  of  the  pure  metals.  A  J  mm.  wire  can  be  made  even  out  of 
pure  gold  or  silver.  Then  the  length  of  wire  required  for 
each  case  is  calculated.  This  is  more  convenient  and  more 
correct  than  direct  weighing,  since  only  from  TV  to  J  gram  of 
an  alloy  is  required  for  a  determination,  and  even  if  a  larger 
stock  of  alloys  is  to  be  made,  the  preparation  in  small  quan- 
tities will  yield  a  more  uniform  product. 

TABLE  VIII. 

MELTING    POINTS    OF   ALLOYS. 
Gold-Silver-Alloys. 


Silver. 

Gold. 

Melting  Point. 

Per  cent. 

Per  cent. 

Deg.  Cent. 

100 

954 

80 

20 

975 

60 

40 

995 

40 

60 

1020 

20 

80 

1045 

100 

1075 

Gold-Platinum-Alloys. 


Gold. 

Platinum. 

Melting  Point. 

Per  cent. 
100 

Per  cent. 

Deg.  Cent. 
1075 

95 

5 

1100 

90 

10 

1130 

85 

15 

1160 

80 

20 

1190 

75 

25 

1220 

70 

30 

1255 

65 

35 

1285 

60 

40 

1320 

55 

45 

1350 

50 

50 

1385 

45 

55 

1420 

40 

60 

1460 

35 

65 

1495 

30 

70 

1535 

25 

75 

1570 

20 

80 

1610 

15 

85 

1650 

10 

90 

1690 

5 

95 

1730 

100 

1775 

PYROMETRY  55 

The  alloys  are  made  by  melting  the  metals  upon  chalk  by 
means  of  a  blow-pipe-flame,  which  gives  sufficient  heat  for  the 
silver-gold  alloys;  for  melting  the  platinum-gold  alloys  a  gas- 
oxygen  flame  or  a  flame  obtained  by  blowing  oxygen  into  a 
burning  mixture  of  2  volumes  ether  and  1  volume  alcohol  has 
to  be  used.  For  preventing  the  volatilization  of  gold,  the 
platinum-gold  alloys  are  melted  as  far  as  possible  with  the 
ordinary  blow-pipe  flame,  and  then  for  complete  melting 
exposed  for  a  few  seconds  to  an  oxygen-blast. 

The  molten  metal  beads  when  quickly  cooled  show  a  fine 
crystalline  structure,  and  when  slowly  cooled  a  coarse  crystal- 
line surface  of  netlike  structure.  They  have  a  remarkable 
inclination  for  demixing  (separating),  which  is  accompanied  by 
the  production  of  a  yellow  color,  both  after  slowly  cooling  and 
after  heating  for  some  time  at  a  temperature  near  the  melting 
point.  In  this  case  the  hammered  surface  is  crystalline,  and 
shows  a  yellowish  instead  of  gray  color.  The  alloys  with  from 
15  to  40  per  cent  of  platinum  show  this  variability  frequently 
to  a  marked  degree ;  they  have  then  to  be  remelted  in  the  oxy- 
hydrogen-flame.  The  alloys  of  gold  and  silver  also  become 
crystalline  under  these  conditions,  but  their  surface  remains 
smooth  and  shows  only  more  or  less  brilliant  parts. 

After  melting  the  alloys  are  beaten  flat  with  a  hammer  and 
exposed  to  the  temperature  to  be  measured  in  a  cupola  made 
of  fire-clay  mixed  with  quartz.  Direct  contact  with  reducing 
flames  has  to  be  avoided,  otherwise  a  thin  coating  of  slag  is 
formed  which  considerably  lowers  the  melting  point.  Experi- 
ments have  shown  that  in  such  a  case  an  alloy  containing  47 
per  cent  of  platinum,  that  should  melt  at  1364°  C.,  showed  a 
melting  point  of  only  1247  degrees.  This  is  probably  due  to 
the  absorption  of  silicon,  and  therefore  it  is  necessary,  if  a 
reducing  flame  is  to  be  used,  to  use  a  cupola-base  free  of  quartz. 
i.e.  either  of  pure  magnesia  or  pure  clay. 

(b)  Seger-cones: 

These  are  mixtures  of  quartz,  kaolin,  white  marble  and 
felspar,  and  are  prepared  by  moistening  the  dry  mixture  with  a 
solution  of  arabic  gum,  forming  it  into  triangular  pyramids 
6  cm.  high,  the  sides  of  the  base  being  1.5  cm.  long.  For  lower 
temperatures  part  of  the  kaolin  is  replaced  by  ferric  oxide. 
The  " cones,"  provided  with  a  number  at  the  top,  are  put  into 


56 


HEAT  ENERGY  AND  FUELS 


a  chamotte-dish,  which  is  brought  into  the  room  of  which  the 
temperature  is  to  be  measured.  The  point  at  which  the 
"cone"  begins  to  soften  (at  which  the  sinking  apex  touches 
the  chamotte-base)  is  taken  as  melting  point.  At  higher  tem- 
perature the  entire  cone  melts  together  into  one  mass. 

TABLE  IX. 
COMPOSITION    AND    MELTING    POINTS    OF    SEGER-CONES. 


No. 

1 
2 
3 
4 
5 
6 
7 
8 
9 

10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 


Chemical  Composition  in  Equiv- 
alents. 


Composition. 


Fel- 
spar. 


Marble 


Quartz. 


Ferric 
Oxide. 


Kaolin. 


Melt- 
ing 
Point. 
Deg. 
Cent. 


0.3K20  (0.2Fe2O3) 
0.7CaO(0.3Al203) 
0.3K2O  (0.1Fe2O3) 
0.7CaO  (0.4A12O2) 
0.3K2O  (0.05Fe2O3) 
0.7CaO  (0.45A12O3) 


A  QiO 

2 


5Si0 


'8,  8SiO2 
2O3,  9  SiO2 


31Si02 


39Si02 


83.5 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 

83.55 


35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35.00 

35. 

35.00 

35.00 

35.00 

35.00 

35.00 


66.00 
60.00 
57.00 
54.00 
84.00 
108.00 
132.00 
156.00 
180.00 
204.00 
252.00 
300.00 
348.00 
396.00 
00 
540.00 
612.00 
708.00 
804.00 
900.00 


16.00 
8.00 
4.00 


00468 


12.95 

19.43 

25.90 

25.90 

38.55 

51.80 

64.75 

77.70 

90.65 

116.55 

142.45 

168.35 

194.25 

233.10 

271.95 

310.80 

362.00 

414.40 

466.20 


1150 
1179 
1208 
1227 
1266 
1295 
1323 
1352 
1381 
1410 
1439 
1468 
1497 
1526 
1555 
1584 
1613 
1642 
1670 
1700 


PYROMETRY 


5? 


The  melting  points  given  were  found  as  follows : 

No.  1  melts  at  a  little  higher  temperature  than  the  alloy 
with  90  per  cent  gold  and  10  per  cent  platinum  (melting  point 
according  to  Erhard  and  Schertel  1130°  C.);  its  melting  point 
was  therefore  assumed  to  be  1150°  C. 

No.  20  melts  at  a  lower  temperature  than  platinum;  the 
melting  point  was  therefore  estimated  to  be  1700°  C. 

Assuming,  furthermore,  that  the  melting  points  of  the  20 
cones  followed  each  other  at  equal  intervals  (which  is  actually 
not  correct)  the  interval  between  two  melting  points  following 
each  other  is  calculated  thus : 


1700  -  1150 
19 


=  28.9  degrees. 


Composition  of  the  pyroscopes  of  higher  numbers  of  Seger 
are  given  in  Table  X. 

TABLE  X. 

COMPOSITION    OF    PYROSCOPES    OF    HIGHER    NUMBERS.      (Seger.) 


Nr 

K20 

CaO 

A1203 

SiO2 

21 

0.3 

0.7 

4.4 

44 

, 

22 

0.3 

0.7 

4.9 

49 

[Difference:  0.5  A12O3,  5  SiO2. 

23 

0.3 

0.7 

5.4 

54 

) 

24 

0.3 

0.7 

6.0 

60 

) 

25 

0.3 

0.7 

6.6 

66 

>  Difference:  0.6  A12O3,  6  SiO2. 

26 

0.3 

0.7 

7.2 

72 

) 

27 

0.3 

0.7 

20 

200 

28 

1 

10 

29 

1 

8 

30 

1 

6 

31 



1 

5 

32 



4 

33 

3 

34 

2.5 

35 

2.0 

36 

1.5 

38 

1.0 

Cramer  has  made  melting  cones  for  measuring  lower  tem- 
peratures in  the  brick  industry.  They  can  be  bought  in  two 
sizes  (6  and  10  cm.  high)  from  the  Royal  Porcelain  Factory  in 
Charlottenburg  or  from  the  Chemical  Laboratory  for  Clay 
Industry,  Berlin,  N.  W.,  Kreuz  str.  6. 


58 


HEAT   ENERGY  AND   FUELS 


TABLE   XI. 

COMPOSITION    OF    PYROSCOPES    FOR    LOW    TEMPERATURES. 

Molecules. 


Nr 

K2O 

CaO 

PbO 

A1203 

Fe203 

Si02 

BA 

01 
02 
03 
04 
05 

0.3 
0.3 
0.3 
0.3 
0.3 

0.7 
0.7 
0.7 
0.7 
0.7 

0.3 
0.3 
0.3 
0.3 
0.3 

0.2 
0.2 
0.2 
0.2 
0.2 

3.95 
3.90 
3.85 
3.80 
3.75 

0.05 
0.10 
0.15 
0.20 
0.25 

06 

0  3 

0  7 

0  3 

0  2 

3  70 

0  30 

07 
08 
09 
010 

Oil 
012 
013 
014 

0.3 
0.3 

0.3 
0.3 
Na20 
0.5 
0.5 
0.5 
0  5 

0.7 
0.7 
0  7 
0.7 

0.5 
0.5 
0.5 
0  5 

0.3 
0.3 
0.3 
0.3 

0.8 
0.75 
0.70 
0  65 

0.2 
0.2 
0.2 

•:":: 

3.65 
3.60 
3.55 
3.5 

3.6 
3.5 
3.4 
3  3 

0.35 
0.40 
0.45 
0.5 

1.0 
1.0 
1.0 
1  0 

015 

0  5 

0  5 

0  60 

3  2 

1  0 

016 
017 
018 
019 
020 
021 
022 

0.5 

0.5 
0.5 
0.5 
0.5 
0.5 
0.5 

0.5 
0.5 
0.5 
0.5 
0.5 
0.5 
0.5 

0.55 
0.50 
0.40 
0.30 
0.20 
0.10 

3.1 
3.0 
2.8 
2.6 
2.4 
2.2 
2.0 

1.0 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 

C.  Bischof,  who  thoroughly  investigated  these  pyroscopes, 
found  even  the  highest  melting  point  far  below  that  of  melting 
platinum.  The  melting  points  of  Nos.  13,  14,  15  and  even  17 
are  only  slightly  above  that  of  melting  palladium  (1500°  C.); 
furthermore  these  pyroscopes  show  various  irregularities  among 
themselves.  However,  notwithstanding  these  defects  the  Central 
Association  of  German  Manufacturers  recommended  the  official 
adoption  of  the  Seger-cones,  March  28,  1904. 

The  table  on  following  page  contains  some  new  data  relative 
to  the  melting  temperatures  of  all  these  cones  (measured  with 
Le  Chatelier  pyrometer). 

Only  the  following  of  these  melting  points  are  correctly 
determined:  Nr.  022  melts  at  dark  red  glow,  Nr.  010  at  the 
melting  point  of  silver,  Nr.  1  near  the  melting  point  of  an  alloy 
containing  90  per  cent  gold  and  10  per  cent  platinum,  Nr.  10  at 


PYROMETRY 


59 


the  point  where  felspar  begins  to  soften,  and  Nr.  36  at  about  the 
melting  point  of  platinum.  The  other  temperatures  are  only 
approximate. 


TABLE   XII. 

MELTING    POINTS    OF    PYROSCOPES. 


Nr. 

Deg.  Cent. 

Nr. 

Deg.  Cent. 

N, 

Deg.  Cent. 

022 

590 

02 

1110 

19 

1510 

021 

620 

01 

1130 

20 

1530 

020 

650 

1 

1150 

21 

1550 

019         680 

2 

1170 

22 

1570 

018 

710 

3 

1190 

23 

1590 

017         740 

4 

1210 

24 

1610 

016         770 

5 

1230 

25 

1630 

015         800 

6 

1250 

26       1650 

014 

830 

7 

1270 

27       1670 

013 

860 

0 

O 

1290 

•  28       1690 

012 

890 

9 

1310 

29       1710 

Oil 

920 

10       1330 

30       1730 

010 

950 

11 

1350 

31 

1750 

09 

970 

12 

1370 

32 

1770 

08 

990 

13 

1390 

33 

1790 

07 

1010 

14 

1410 

34 

1810 

06 

1030 

15 

1430 

35       1830 

05 

1050       16 

1450 

36       1850 

04        1070       17 

1470 

38       1890 

03. 

1090        18 

1490 

|  !  

7.  Color  imetric  pyrometers.  With  these  instruments  the 
temperature  is  derived  from  the  quantity  of  heat  that  is 
given  off  by  a  heated  body  when  cooling  off  in  the  calorimeter. 
This  method  was  strongly  recommended  by  Pouillet,  Regnault, 
Carnelley,  Violle  and  others,  and  introduced  into  industrial 
practice  by  Weinhold,  Fiodier  and  others. 

In  order  to  reduce  the  radiation  heat  losses  from  the  calo- 
rimeter to  a  minimum,  the  instrument  is  so  designed  that  it 
becomes  only  slightly  heated.  In  an  apparatus  to  be  used  for 
scientific  purposes  the  temperature  rise  of  the  calorimeter  is 
measured  by  a  mercury  thermometer  comprising  2  degrees 
and  divided  into  T£^  degrees. 

At  first  an  iron  cylinder  was  used  as  the  thermometric  sub- 
stance, i.e.,  the  substance  which  gives  off  the  heat  to  be  measured 
in  the  calorimeter.  The  use  of  iron,  however,  proved  to  be 


60 


HEAT   ENERGY  AXD  FUELS 


unsatisfactory  on  account  of  its  easy  oxidation  and  of  its  non- 
uniform  cooling.  If  we  take  the  heat  given  off  and  the  tem- 
perature as  co-ordinates,  we  obtain  a  curve  with  two  points  of 
inflexion,  corresponding  to  the  allotropic  change  of  state  of 
the  iron.  This  shows  that  the  temperatures  calculated  could 
not  be  correct. 

This  is  the  reason  why  platinum  substances  and  a  mercury- 
thermometer  divided  in  T£7  degrees  are  used  in  laboratories, 
and  in  the  industries  a  nickel-cylinder  (the  heating  of  this 
metal  is  very  regular)  and  a  mercury-thermometer  divided  in 
TV  degrees  whose  scale,  therefore,  can  be  larger.  A  rise  of 
about  50°  C.  in  the  calorimeter-temperature  is  sufficiently  exact 
for  practical  purposes.  The  nickel-cylinder  is  put  into  a  small 
pipe  of  fire-proof  material,  fitted  with  a  removable  iron  handle. 
After  the  pipe  with  the  cylinder  has  been  in  the  furnace  whose 
temperature  is  to .  be  measured  for  fifteen  minutes,  one  can  be 
sure  that  equilibrium  of  temperature  has  been  established. 
The  pipe  is  now  taken  out  of  the  furnace,  emptied  into  the 
calorimeter,  the  calorimeter-water  stirred  and  the  increase  of 
temperature  read  and  recorded. 

The  following  tests  made  by  the  Compagnie  Parisienne  du 
Gaze  show  the  regularity  of  the  heating  law  for  nickel : 

tCJ   =    50.5    63.5    89.5    103     117.5    134     150    166 
t   =  400°    500°    700°    800°    900°  1000°  1100°  1200° 

We  give  below  a  few  melting  temperatures  determined  by 
Violle  and  also  by  Holborn  and  Day. 


TABLE  XIII. 

MELTING    POINTS    OF    METALS. 


Metal. 

Violle. 

Holburn  arid 
Day. 

Silver 

Degrees 
954 

Degrees 
961  5 

Gold        

1045 

1064 

Copper  

1055 

1065 

Palladium  

1500 

1500 

Platinum  .  . 

1779 

1780 

PYROMETRY 


61 


Below  we  describe  a  few  pyro-calorimeters  that  were  con- 
structed for  practical  use. 

The  latest  type  of  Weinhold's  pyrometer  for  determining 
high  temperatures  is  illustrated  in  Fig.  7.  The  calorimeter- 
vessel  proper  CC  is  made  of  thin  sheet  brass.  It  holds  about 
1  Kg  of  water,  is  cylindrical  at  the  bottom  and  conical  at 


FIG.  7.  —  WeinhokTs  Pyrometer. 

the  top.  The  ratio  of  the  height  to  the  diameter  is  so  chosen 
as  to  make  the  surface  as  small  as  possible,  in  order  to  reduce  to 
a  minimum  the  loss  or  gain  of  heat  by  radiation  or  conduc- 
tion. A  cylindrical  vessel  of  tin-plate  BE  with  a  loose  conical 
cover  DD  surrounds  the  calorimeter- vessel,  which  is  carried 
by  three  cork-pieces,  cemented  into  BB,  and  so  arranged  as  to 
maintain  a  space  of  1  cm.  between  the  walls  of  the  containing 
vessel  and  the  calorimeter.  BB  is  fastened  in  a  wooden  box 
HH.  As  wood  and  still  air  are  very  poor  conductors  of  heat, 
and  as  bright  sheet  metal  prevents  radiation  of  heat,  by  this 
method  an  excellent  heat-insulation  is  effected.  The  center 


62 


HEAT   ENERGY  AND  FUELS 


one  of  the  three  cylindrical  openings  in  the  calorimeter- 
vessel  serves  for  introducing  -the  metal  ball,  which  is  bored 
through  in  three  directions  perpendicular  to  each  other.  The 
thermometer  T  is  inserted  through  a  cork  in  the  shortest  neck. 
The  shaft  of  the  circulating  device  R  is  inserted  through  the 
narrow  neck.  This  device  (Fig.  8)  consists  of  an  impeller  with 
six  inclined  paddles  which  move  in  a  slim  brass  tube,  open  at 
the  top  and  the  bottom.  Its  shaft  is  rectangular  at  the  top, 


FIG.  8.  —  Circulating  Device  (for  7). 


FIG.  9.  —  Brass  Wire  Basket. 


so  that  the  pulley  S  can  be  attached.  By  means  of  a  cord 
passing  over  three  guide-pulleys  and  a  crank  wheel,  attached 
to  the  outside  of  the  wooden  box,  R  can  be  rapidly  rotated. 
The  lively  circulation  of  water  caused  thereby  facilitates  the 
equalization  of  the  temperature  in  the  calorimeter.  The 
thermometer  T  is  provided  with  a  scale  divided  in  0.1  degrees, 
on  which,  however,  0.01  degrees  can  be  estimated.  The  thin 
cylindrical  mercury-reservoir  of  the  thermometer  (50  to  60 
mm.'s  long)  extends  nearly  the  entire  height  of  the  calorimeter. 
The  hot  metal  ball  is  kept  in  the  brass- wire  basket  (Fig.  9). 
Its  cover  can  be  turned  around  a  hinge,  and  is  provided  with  a 
pin  attached  rectangularly  downward.  If  the  basket  —  with 


PYROMETRY  63 

the  cover  open  —  is  let  down  into  the  neck  of  the  calorimeter, 
the  cover  —  and  also  the  basket  —  remain  hanging  upon  the 
edge  of  the  neck.  If  now  the  ball  is  allowed  to  fall  through 
the  neck,  it  hits  the  pin  and  thereby  closes  the  cover.  This 
causes  the  basket  with  the  ball  to  fall  upon  the  bottom  of  the 
calorimeter,  so  that  finally  the  cover  almost  touches  the  surface 
of  the  water,  which,  before  putting  in  the  basket  and  the  ball, 
should  reach  to  the  lower  edge  of  the  neck.  To  assure  the  right 
amount  of  water  in  the  calorimeter,  a  pipette  is  used,  which  is 
fastened  to  a  disk  of  metal,  wood,  or  cork,  so  that  its  lower  end 
is  exactly  flush  with  the  entry  of  the  neck  to  the  calorimeter. 
At  first  water  is  put  in  until  it  stands  a  few  millimeters  high  in 
the  neck,  then  the  disk  of  the  pipette  is  laid  upon  the  edge  of 
the  neck  and  the  excess  water  sucked  out. 

By  throwing  the  hot  ball  into  the  calorimeter  not  only  the 
water  contained  in  the  latter  but  also  the  calorimeter-vessel  is 
heated  up.  To  determine  the  quantity  of  heat  absorbed  by  the 
instrument,  the  quantity  of  heat  absorbed  by  the  vessel  has  also 
to  be  considered.  This  is  done  by  ascertaining  the  quantity 
of  water  that  would  be  necessary  to  absorb  the  same  quantity  of 
heat  as  the  calorimeter,  i.e.,  by  determining  the  water- value  of 
the  calorimeter.  For  this  purpose  the  brass  calorimeter-vessel, 
together  with  the  stirring  arrangement  and  the  basket  K  (but 
without  the  pulley  S  and  thermometer  T  with  cork)  is  weighed  in 
a  dry  state.  The  weight  found,  multiplied  by  the  specific  heat 
of  brass  (0.095) ,  gives  the  water- value  of  the  empty  calorimeter. 
The  water-value  of  the  thermometer  is  difficult  to  find,  but  can 
be  neglected  on  account  of  the  small  quantity  involved.  After 
inserting  the  thermometer  with  the  cork  the  apparatus  is  weighed 
a  second  time,  and  finally  after  putting  in  the  cooling  water  it  is 
weighed  for  the  third  time.  The  difference  of  the  second  and 
third  weight  gives  the  water  content  of  the  calorimeter.  The 
water-value  of  the  filled  calorimeter  is  the  sum  of  this  water 
content  and  the  water-value  of  the  empty  calorimeter.  If,  for 
instance,  the  empty  calorimeter  without  thermometer  weighs 
210  g.,  with  thermometer  236  g.,  with  water  1240  g.,  we  have: 

Water  value  of  the  empty  calorimeter  =  210  X  0.095  =  19.95  g. 
Water  content  of  the  calorimeter  =1240-  236  =  1004.00  g. 
Water  value  of  the  filled  calorimeter  =  1004  +  19.95  =  1023.95  g. 


64  HEAT  ENERGY  AND  FUELS 

The  water-value  of  the  empty  calorimeter  is  more  conveniently 
determined  by  putting  into  the  instrument  a  weighed  quantity 
of  water,  then  throwing  in  a  test  ball  of  a  certain  temperature 
(for  instance  100°  C.)  and  measuring  the  increase  of  temperature. 
If  we  divide  the  heat  given  off  by  the  ball  by  the  increase  of  tem- 
perature and  deduct  therefrom  the  weight  of  the  calorimeter,  we 
obtain  the  water-value  of  the  dry  instrument. 

The  balls  used  weigh  from  60  to  80  g.  For  introducing  them 
into  the  space,  the  temperature  of  which  is  to  be  measured,  a 
pair  of  tongs  made  of  heavy  iron  wire  or  bar  iron,  provided  with 
cup-shaped  jaws,  is  used  (Fig.  10) ,  or  a  spoon  with  cover,  and  fitted 


FIG.  10.  —  Tongue.  FIG.  11.  —  Spoon. 

with  a  long  handle  (Fig.  11).  The  weight  of  the  ball  has  to  be 
determined  before  use.  If  the  balls  are  of  the  size  mentioned  it 
is  sufficiently  accurate  to  weigh  to  the  nearest  decigrams. 

When  using,  the  calorimeter  is  filled  with  fresh  water,  the  wire 
basket  put  in,  and  —  immediately  before  inserting  the  ball  - 
the  circulation  device  is  started,  and  kept  in  motion  until  the 
thermometer  shows  a  constant  temperature,  which  is  read  and 
recorded  (initial  temperature  of  the  calorimeter).  When  intro- 
ducing the  ball,  care  has  to  be  taken  not  to  injure  the  thermometer 
and  the  driving  cord  of  the  circulation  device.  Directly  after 
throwing  in  the  ball,  the  circulation  device  is  worked  until  the 
thermometer  becomes  stationary  when  the  temperature  (final 
temperature)  is  read  and  recorded. 

The  difference  between  initial  and  final  temperature  multiplied 
by  the  water-value  of  the  filled  calorimeter  —  expressed  in  kilo- 
grams —  gives  the  heat-quantity  (in  calories)  transmitted  from 
the  ball  to  the.  calorimeter.  Therefrom  the  quantity  of  heat 
given  off  by  a  1  Kg.  ball  is  calculated,  and  by  comparing  this 
figure  with  a  table  in  which  the  heat  (c.  t.)  is  calculated  from 
the  specific  heat  of  the  metal,  the  temperature  is  found. 

Considerably  simpler  in  construction  is  the  calorimeter  of  Dr. 
Ferdinand  Fischer  (Fig.  12).  The  cylinder  A,  which  is  made  of 
thin  copper  plate  and  has  a  diameter  of  500  mm.,  is  suspended 


PYROMETRY 


65 


in  the  wooden  base  B.  The  space  between  both  is  filled  with 
fibrous  asbestos  or  mineral  wool.  The  apparatus  is  closed  by  a 
thin  brass  or  copper  plate,  having  a  large  opening  d  (20  mm. 
diam.)  for  the  stirrer  c  and  for  throwing  in  the  metal  cylinder, 
and  a  small  opening  for  the  thermometer  6,  which  is  a  normal 
thermometer  built  by  Geissler 
in  Bonn.  It  has  a  very  small 
mercury  reservoir;  its  scale  has 
a  range  of  from  0°  to  50°  C.,  and 
is  divided  into  0.1  degrees,  so 
that  0.01  degrees  can  easily  be 
estimated ;  a  strap  a  of  thin  cop- 
per plate  protects  it  from  being 


FIG.  12.  —  Fischers  Calorimeter.  FIG.  13.  —  Siemens  Water  Pyrometer. 

broken  by  the  stirrer.  The  stirrer  consists  of  a  round  copper  disk, 
soldered  to  a  copper  rod.  The  latter  is  melted  into  a  glass  rod, 
that  serves  as  handle.  If,  for  instance,  the  copper  vessel  weigh 
35.905  g.,  the  stirrer  without  glass  rod  weigh  6.445  g.,  then  the 
water-value  of  the  calorimeter  is  0.094  (35.905  +  6.445)  -  3.98  g., 
including  the  thermometer  about  4  g.  If  the  calorimeter  water 
weigh  246  g.,  the  water-value  of  the  filled  calorimeter  is  250  g. 


66 


HEAT  ENERGY  AND  FUELS 


For  measuring  the  temperature  doubly  bored  cylinders  of  plati- 
num, wrought  iron  or  nickel  are  used.  For  the  first  case,  i.e.,  with 
platinum  cylinders  weighing  20  g.,  such  a  quantity  of  water  is 
put  in  that  the  total  water- value  amounts  to  about  125  g.,  with 
the  two  other  metals  to  twice  that  amount.  In  a  manner  similar 
to  that  given  above  the  cylinders  are  exposed  in  the  medium 
the  temperature  of  which  is  to  be  measured  and  thrown  into  the 
calorimeter  through  the  cover  opening  d.  The  cylinder  falls 
upon  the  disk  of  the  stirrer,  and  now  by  raising  and  lowering  the 
latter  a  uniform  heating  of  the  calorimeter-water  is  effected,  so 
that  at  the  end  of  about  one  minute  the  thermometer  reaches 
the  final  temperature. 

No  corrections  are  made  for  evaporation  of  water  or  heat 
transmission  by  radiation  or  conductivity,  as  the  evaporation  is 
extremely  small  and  the  insulation  of  the  calorimeter  perfect. 
If  the  calorimeter-water  reaches  a  temperature  of  about  40  de- 
grees it  has  to  be  changed.  The  calculation  of  the  temperature 
is  made  as  in  the  former  case. 

TABLE   XIV. 

HEAT    CAPACITIES    OF    PLATINUM,    ETC. 


I  kit  iuu  in 

Iron. 

Nickel. 

t°c. 

According 
to  Violle. 

Post. 

Pion- 

chon. 

Eu- 
chenne. 

Calculated 
from  the 
Average 
Specific 

Pion- 
chon. 

Eu- 
ch£nne. 

Heat. 

cal. 

cal. 

cal. 

cal. 

cal. 

cal. 

cal. 

100 

3.23 

10.8 

11.0 

11.0 

10.8 

11.0 

12.0 

200 

6.58 

22.0 

22.5 

23.0 

21.5 

22.5 

24.0 

300 

9.75 

35.0 

36.5 

37.0 

32.5 

42.0 

37.0 

400 

13.64 

39.5 

41.5 

42.0 

43.0 

52.0 

50.0 

500 

17.35 

67.5 

68.6 

69.5 

54.0 

65.5 

63.5 

600 

21.18 

86.0 

87.5 

84.0 

65.0 

78.5 

75.0 

700 

25.13 

108.0 

111.5 

106.0 

76.0 

92.5 

90.0 

800 

29.20 

132.0 

137.0 

131.0 

87.0 

107.0 

103.0 

900 

33.39 

157.0 

157.5 

151.5 

98.0 

123.0 

117.5 

1000 

37.7 

187.5 

179.0 

173.0 

109.0 

138.5 

134.0 

1100 

42.13 

150.0 

1200 

46.65 

166.0 

1300 

51.35 



1400 

56.14 

1500 

61.05 

1600 

66.08 

1700 

71.23 

1800 

76.50 

• 

PYROMETRY  67 

One  of  the  simplest  and  oldest  but  also  most  widely  used  instru- 
ments is  the  water-pyrometer  of  C.  H.  Siemens  (Fig.  13).  It  con- 
sists of  a  copper  vessel  A  holding  568  cu.  cm.  of  water.  In  order 
to  reduce  the  loss  by  radiation  it  is  surrounded  by  two  vessels, 
one  being  filled  with  felt,  the  other  being  empty.  The  mercury 
thermometer  is  protected  by  a  perforated  metal-shell  and  has 
besides  the  ordinary  scale  a  movable  brass  scale  c  (similar  to  a 
vernier),  that  gives  the  temperature  directly  without  calculation. 
After  filling  the  calorimeter  with  water  the  zero  mark  of  the 
pyrometer-scale  is  set  upon  the  temperature  of  water,  as  shown 
by  the  mercury  thermometer.  A  hollow  copper  cylinder  of  a 
certain  heat-capacity  is  now  exposed  in  the  medium,  the  tem- 
perature of  which  is  to  be  measured,  and  after  remaining  there 
10  to  15  minutes  is  thrown  into  the  calorimeter- water. 

The  temperature  required  is  obtained  by  adding  to  the  tem- 
perature read  off  the  pyrometer-scale  c,  the  temperature  of  the 
calorimeter- water.  The  manipulation  of  this  instrument  is  there- 
fore extremely  simple,  naturally  at  the  expense  of  accuracy. 

For  calculating  the  temperatures  the  following  data  of  the 
heat  capacities  of  platinum,  iron  and  nickel  from  0  degrees  to 
t  degrees  can  be  used. 


CHAPTER   III. 
PYROMETRY   (Conclusion). 
OPTICAL  METHODS  OF  MEASURING  TEMPERATURES. 

THE  instruments  used  for  this  purpose  are  based  upon  the 
relation  between  temperature  and  emission  of  light  from  heated 
substances. 

(a)  If  a  substance  is  gradually  heated  up,  it  starts  at  a  certain 
temperature  to  emanate  light-rays,  the  brightness  of  the  latter 
increasing  with  the  temperature.  The  color  of  the  emanated 
light  changes  in  a  definite  manner  with  the  temperature.  In 
many  industries,  after  some  practice,  the  approximate  tempera- 
ture of  a  furnace  can  be  estimated  with  the  naked  eye  without 
any  instruments,  from  the  brightness  of  the  glowing  walls  and 
the  heated  substances. 

The  oldest  data  relative  to  the  temperature  of  these  so-called 
glow-colors  were  given  by  Pouillet. 

The  temperatures  of  the  glow-colors  have  been  determined  by 
means  of  a  Le  Chatelier-Pyrometer,  by  Maunsel  White  and  F.  W. 
Taylor,  and  by  Howe.  The  table  on  following  page  contains  the 
results  of  these  investigations. 

The  extreme  rays  of  the  spectrum  show  plainly  the  changes 
of  brightness  and  color;  but  the  yellow  rays  in  the  center,  on 
account  of  their  brightness,  cover  up  all  the  others.  The  experi- 
ment was  therefore  tried  of  absorbing  the  latter  by  means  of  blue 
cobalt-glass.  A  glowing  substance,  viewed  with  such  a  glass, 
appears  at  relatively  low  temperature  very  red,  and  at  high 
temperature  strongly  blue;  thence  with  this  method  more 
reliable  results  are  obtained  than  with  the  naked  eye. 

(6)  The  optical  pyrometer  of  Mesure  and  Nouel  (Figs.  14,  15) 
can  be  obtained  from  E.  Ducretet  in  Paris. 

The  direct  observation  of  the  glow-colors  is  rather  difficult 
since  it  depends  on  individual  qualification  and  momentary  dis- 
position. The  eye  can  never  determine  the  color  shades  with 


PYROMETRY 


absolute  exactness,  being  only  able  to  estimate  by  comparison. 
In  a  dark  furnace-room  the  dark  red  of  a  melting  metal  can 
easily  be  taken  as  bright  red,  and  vice  versa  in  a  light  room,  so 


FIGS.  14  and  15.  —  Lunette  Pyrome'trique  (Pyroscope). 

that  the  result  of  such  observation  varies  according  to  observer, 
light  and  time  of  observation. 

TABLE   XV. 
TEMPERATURES    CORRESPONDING    TO    GLOW    COLORS. 


Pouillet. 

Howe. 

White  and  Taylo 

r. 

Heat  Color. 

Deg. 
Cent. 

Heat  Color. 

Deg. 
Cent. 

Heat  Color. 

Deg. 
Cent. 

Beginning  glow  . 
Dark  red  glow  .  . 
Beginning 
cherry  red. 
Cherry  red  
Bright   cherry 
red. 
Dark  yellow.  .  .  . 

525 
700 

800 
900 
1000 

1100 

First  trace  (  in  dark 
of  visible  < 
red             (  in  daylight 

?  Dark  red  < 

Full  cherry  red  
Bright  red  

470 
475 

550 
to 
625 
700 
850 

Dark  red  
Dark  cherry  .  .  . 

Cherry  red  
Bright  cherry.  . 

Orange  

566 
635 

746 

843 

899 

Bright  yellow.  .  . 

1200 

Full  yellow                     < 

950 
to 

Bright  orange  . 

941 

White  glow  
Bright  white.  .  .  . 

1300 
1400 

Bright  yellow  
White  glow 

1000 
1050 
1150 

Yellow  
Bright  yellow.  . 
White  glow.  .  .  . 

996 
1079 
1205 

Dazzling  white  < 

1500 
to 
1600 

The  object  of  the  pyrometric  tube  of  Mesure  and  Noue'l  is 
the  correction  of  this  defect;  it  allows  the  determination  of  the 


70  HEAT   ENERGY   AND  FUELS 

temperature  of  a  substance  by  simple  observation  and  enables 
us  to  determine  more  distinctly  the  shade  of  the  color. 

The  apparatus  is  based  upon  the  phenomenon  of  circular 
polarization  and  consists  mainly  of  two  Nicol-prisms,  the  polarizer 
P  and  the  analyzer  A.  Between  these  two  prisms  is  arranged  a 
quartz-disk  Q,  11  mm.  thick,  split  perpendicularly  to  the  main- 
axis.  At  the  zero  position  of  the  instrument  the  planes  of  inci- 
dence of  the  two  Nicol-prisms  are  perpendicular  to  each  other. 
The  correctness  of  the  position  of  the  prisms  can  easily  be 
verified  by  taking  off  Af ,  and  removing  the  quartz-disk.  Oppo- 
site to  the  eye-piece  L  at  the  other  end  of  the  tube  is  the 
objective  G,  consisting  of  a  plane-glass  or  a  well-polished  diverg- 
ing glass. 

The  following  phenomenon  can  be  observed  by  looking  with 
this  apparatus  towards  a  source  of  light.  After  passing  through 
the  Nicol-prism  P  the  light  is  polarized.  Without  a  quartz- 
plate,  i.e.  with  the  second  (perpendicular  to  the  first)  Nicol- 
prism  following  the  first,  this  polarized  light  would  be  reflected 
by  the  cut  surface  of  the  Nicol-prism,  and  the  field  of  view  would 
appear  dark.  The  quartz-plate,  however,  causes  a  turning  of 
the  plane  of  polarization  that  is  proportional  (according  to  Biot's 
law)  to  the  thickness  of  the  quartz-plate  and  approximately 
inversely  proportional  to  the  wave  length  of  the  ray  (light). 
Thereby  certain  colors  of  the  spectrum  are  extinguished  by 
interference,  and  a  mixed  color  is  observed  in  the  apparatus,  de- 
pending on  the  temperature  of  the  luminous  body.  By  turning 
the  analyzer  the  mixed  color  is  changed,  and  whenever  the  instru- 
ment is  set  upon  the  same  color-shade  the  temperature  of  the 
substance  under  observation  can  be  inferred  from  the  position  of 
the  polarizer.  For  this  purpose  the  analyzer  inside  the  tube  is 
made  so  that  it  can  be  rotated.  For  measuring  the  displacement 
angle  the  instrument  has  a  fixed  mark  /  and  is  provided  with  a 
scale  that  can  be  rotated  with  the  eye-piece  and  the  analyzer. 
Since  the  length  of  the  wave  of  the  emitted  light  varies  with  the 
temperature,  by  slowly  turning  the  analyzer  certain  colors  that 
are  changing  with  the  temperature  of  the  luminous  body  can  be 
observed.  The  change  from  one  color  to  another  corresponds  to 
a  certain  displacement-angle,  varying  with  the  temperature  of 
the  glowing  substance. 

Hereby  we  arrive  at  a  position  where  the  color,  by  the  slightest 


PYROMETRY 


71 


further  rotation,  changes  quickly  from  blue  to  red.  Between 
these  two  colors  is  observed  a  purple-violet  shade  formed  by  the 
most  extreme  rays  of  the  spectrum;  this  shade  is  character- 
istic for  measuring  the  angle  of  displacement.  (Another  shade 
[lemon-yellow],  between  green  and  red,  can  also  be  used  for  this 
purpose.)  The  position  of  hand  I  on  the  graduated  arc  C  gives 
the  angle  from  which  the  temperature  is  figured. 

For  determining  the  scale  of  temperature  Pouillet's  data  on 
glow  temperatures  and  the  melting  point  of  silver  (954°  C.)  and 
platinum  (1775°  C.)  according  to  Violle  are  used. 


TABLE  XVI. 
GLOW    TEMPERATURE    OF    SILVER. 


Heat. 

Displace- 
ment. 

Tempera- 
ture, Cent. 

Color: 
Beginning  cherry  red  
Cherry  red  

Degrees. 
33 
40 

Degrees. 
800 
900 

Bright  cherry  red  

46 

1000 

Orange 

52 

1100 

Yellow 

57 

1200 

Bright  yellow  
Bright  white  
Dazzling  white  
Dazzling  white  
Dazzling  white          

62 
66 
69 

71-72 
73-74 

1300 
1400 
1500 
1600 
1700 

Sunlight  :  

84 

8000 

Below  are  given  the  results  of  some  measurements  with  this 
instrument : 

TABLE   XVII. 

DATA    ON    POLARISCOPIC    PYROMETERS. 


(A)  Measurements  by  the  Author. 

Angle. 

Tempera- 
ture, Cent. 

Bessemer  steel  in  the  pan   

Degrees. 
59 

Degrees. 
1260 

Open-hearth  furnace,  empty  

61.75 

1290 

"     after  charging  the  above  steel  
"    middle  of  charge  
"         "             "     towards  end  of  charge 

59.5 
58.5 
63  5 

1275 
1245 
1340 

Heating  furnace  

50.5 

1050 

HEAT   ENERGY  AND  FUELS 


(E)  Measurements  of  J.  Weiler  in  the  Bessemer  converter: 

Deg.  Cent. 

While  blowing . 1330 

At  the  end .  . .  . 1580 

Slag 1580 

Steel  in  pan 1640 

•Preheated  block.. 1200 

Block  under  hammer 1080 

Blast  furnace  for  gray  iron : 

Beginning  of  melting  zone 1400 

Steel  crucible  furnace 1600 

Brick  kiln 1100 

Heat  colors :  red  heat 525 

Cherry 800 

Orange ' 1100 

White 1300 

Dazzling  white. 1500 

(C)  Measurements  of  Le  Chatelier: 

Angle.  Deg.  Cent. 

Degrees. 

Sun 84-86  8000 

Gas-flame 65-70  1680 

Red  glowing  platinum 40-45  800 


To  keep  out  side-light  it  is  of  advantage  to  fasten  a  protecting 
tube  in  front  of  the  objective.  For  the  determination  of  low 
temperatures  a  convergent  lens  is  placed  before  the  instrument. 

(c)  Temperature  can  also  be  judged  from  the  proportion  of 
the  intensities  of  two  certain  kinds  of  rays  (for  instance  red  and 
green)  that  are  emitted  from  the  heated  substance. 

Table  XVIII  gives  the  difference  of  the  emission  of  red, 
green  and  blue  rays  of  different  substances  compared  to  a  black 
substance. 

Crova  has  constructed  a  pyrometer  based  upon  these  data; 
however,  it  requires  very  great  care  in  manipulation. 

(d)  Analogously  the  intensity  of  a  single  ray  of  a  certain  wave 
length  can  be  used  for  measuring  temperature.     One  would  think, 
at  the  first  thought,  that  the  intensity  depends  on  the  emitting 


PYROMETRY 


73 


capacity  of  the  glowing  substance,  this  capacity  varying  widely 
as  is  shown  by  the  above  figures.  Actually,  however,  with  most 
substances  the  variation  in  the  emission  is  equalized  by  the 
capacity  of  reflection,  which  varies  in  the  opposite  sense.  Fur- 
thermore the  capacity  of  emission  of  most  of  the  substances  used 
in  the  industries  is  not  considerable. 

TABLE  XVIII. 

EMISSIVE    POWER    OF    VARIOUS    SUBSTANCES. 


Deg. 
Cent. 

Red. 

Green. 

Blue. 

Magnesia         .                        

1300 

0  10 

0  15 

0  20 

Magnesia   

1550 

0.30 

0.35 

0.40 

Lime  

1200 

0.05 

0.10 

0.10 

Lime  

1700 

0.60 

0.40 

0.60 

Oxide  of  chromium 

1200 

1  00 

1  00 

1  00 

Oxide  of  chromium 

1700 

1  00 

1  40 

0  30 

Oxide  of  thorium 

1200 

0  50 

0  50 

0  70 

Oxide  of  thorium                           

1760 

0  60 

0  50 

0  35 

Oxide  of  cerium               

1200 

0  8 

1  00 

1  0 

Oxide  of  cerium        

1700 

0  9 

0  90 

0  85 

Welsbach  mixture          

1200 

0  25 

0  40 

1.0 

Welsbach  mixture           

1700 

0  50 

0  80 

1.0 

The  Cornu-Le  Chatelier  optical  pyrometer  is  based  upon  this 
principle  (Fig.  16).  The  instrument  takes  the  form  of  a  tube, 
through  which  the  glowing  substance  is  viewed.  A  reflector 


FIG.  16.  —  Optical  Pyrometer  (Cornu-Le  Chatelier). 

consisting  of  a  glass-plate  with  parallel  faces  throws  the  image 
of  a  small  flame  into  the  eye-piece.  A  red  glass  in  front  of  the 
eye-piece  cuts  off  all  but  certain  rays.  Absorbing  glasses  can 
be  put  in  front  of  the  objective  glass,  so  that  only  ^  of  the 


74 


HEAT   ENERGY  AND  FUELS 


incident  light  is  allowed  to  go  through.  Between  these  glasses 
and  the  objective  a  transparent  piece  of  onyx  (Fig.  17)  is  inserted 
by  means  of  which  the  light  can  be  reduced 
at  will.  The  observation  is  made  by 
reducing  the  red  light  of  the  glowing  sub- 
stance, whose  temperature  is  to  be  deter- 
mined, by  means  of  the  darkening  glasses 
and  the  onyx,  until  it  is  equal  in  brightness 
lamp.  The  apparatus  is  calibrated  by  direct 
By  this  method  the  follow- 


loo 


FIG.  17.  —  Piece  of  Onyx 
for  Reducing  the  Light. 


to  the  standard 

comparison  with  an  air-pyrometer. 

ing  intensities  of  light  (red  rays  A  =  659)  were  measured : 


TABLE   XIX. 
INTENSITIES    OF    LIGHT. 


Red  -glowing  coal  (600°)  .... 
Melting  silver  (950°)  
Stearine  candle,  gas  burner 
Pigeon  lamp  ... 

0.0001 
0.015 
1 
1  1 

Melting  palladium  (1550) 
Melting  platinum  
Incandescent  lamp  
Arc  light 

4.8 
15 
40 
10000 

Argand  burner  with  glass  .  . 
Welsbach  burner  

1.9 

2.05 

Sunlight  (noon)  
Melting  Fe2O3  (1350°).... 

90000 
2.25 

By  this  method  at  first  a  thermo-element  was  calibrated,  by 
means  of  which  the  intensity  of  emission  of  black  ferric  oxide 
at  different  temperatures  was  determined.  It  was  found  that 
the  law  for  the  change  of  intensity  of  the  red  rays  with  the 
temperature  can  be  expressed  by  the  formula  : 


3210 

T 


wherein  T  is  the  absolute  temperature.     The  following  intensities 
(in  candlepower)  were  obtained  for  different  temperatures  : 

TABLE   XX. 
LIGHT    INTENSITIES    FOR    VARIOUS    TEMPERATURES. 


Intensity. 

Temperature  in  Deg. 
Cent. 

Intensity. 

Temperature  in  Deg. 
Cent. 

0.00008 

600 

39.0 

1800 

0.00073 

700 

60.0 

1900 

0.0046 

800 

93.0 

2000 

0.020 

900 

1800 

3000 

0.078 

1000 

9700 

4000 

0.24 

1100 

28000 

5000 

0.64 

1200 

56000 

6000 

1.63 

1300 

100000 

7000 

3.35 

1400 

150000 

8000 

6.7 

1500 

224000 

9000 

12.9 

1600 

305000 

10000 

22.4 

1700 

PYROMETRY  75 

As  can  be  seen  from  this  table  the  intensities  increase  rapidly. 
Hence,  if  in  the  determination  of  high  temperatures  an  error  of 
0.1  candlepower  is  made  in  the  measurement,  the  error  in  the 
temperature  does  not  amount  to  more  than  from  2  to  3°  C., 
which  error  can  be  entirely  neglected. 

The  flame  in  the  furnace  must  be  avoided  during  the  obser- 
vation as  otherwise  incorrect  results  are  obtained.  This  method 
is  very  good  for  measuring  high  temperatures,  it  is  less  exact, 
however,  for  low  temperatures. 

Le  Chatelier  made  the  following  measurements  with  this 
instrument : 

TABLE   XXI. 

TEMPERATURE    DETERMINATIONS    (Le   Chatelier). 


Deg.  Cent. 

Open-hearth  steel  furnace 1490  to  1580 

Glass  furnace 1375  to  1400 

Porcelain  furnace 1370 

Porcelain  furnace,  new 1250 

Incandescent  lamp 1800 

Arc  light 4100 

Sunlight 7600 

Blast  Furnace. 

Deg.  Cent. 

At  the  tuyeres 1930 

Pig  iron,  beginning 1400 

Pig  iron,  end 1520 

Bessemer   Process. 

Deg.  Cent. 

Slag 1580 

Steel  flowing  into  pan 1640 

Reheating  of  ingot 1200 

End  of  forging 1080 

Open-hearth  steel: 

Steel  flowing,  beginning 1580 

Steel  flowing,  end 1420 

Casting  into  form 1490 


Fery  has  made  some  changes  in  this  instrument. 
Wanner's  optical  pyrometer  is  based  upon  the  same  principle. 
If  we  denote  the  intensity  (of  light)  as  /,  the  length  of  wave  as 


76  HEAT   ENERGY  AND  FUELS 

i 

X,  the  absolute  temperature  as  T  and  two  constants  as  c^  and  c2, 
we  have,  according  to  Wien  : 

c         c* 
T  -  J-  P    AT  . 

"/I5 

As  we  have  no  absolute  measure  for  the  intensity,  we  can  only 
compare  same  with  another  luminous  body;  for  the  latter  we 
have 


and  therefore 


an  equation  containing  only  one  constant.  This  equation  is 
perfectly  correct  only  for  absolutely  black  bodies,  but  can  also 
be  used  for  measuring  temperatures  in  a  furnace  —  on  account 
of  the  reflection  going  in  all  directions  in  the  interior  of  the 
furnace. 

When  determining  flame  temperatures  great  care  has  to  be 
taken.  If  the  flame  temperature  is  the  same  as  that  of  the 
surrounding  furnace-  walls,  this  method  can  be  used  as  it  is;  if, 
however,  only  glowing  gases  are  present,  colored  for  instance  by 
sodium,  correct  furnace  temperatures  are  not  obtained  except 
when  the  flame  allows  the  rays  used  in  the  measurement  to  pass 
unabsorbed.  Converter-gases  are  rather  opaque  to  red  (the 
color  used  in  the  Wanner  pyrometer),  especially  so  when  many 
solid  particles  are  burning  in  the  flame.  Hence  too  low  a 
temperature  will  be  obtained. 

In  the  optical  pyrometer  the  light  is  decomposed  by  a  straight 
prism,  and  by  means  of  a  small  slit  nothing  but  the  light  corre- 
sponding to  Frauenhofer's  line  c  is  allowed  to  go  through.  As, 
according  to  above  equation,  the  measurement  of  temperature 
is  based  upon  the  comparison  of  two  luminous  substances,  a 
small  electric  lamp  is  used  as  the  standard  luminous  body.  The 
lamp  is  attached  to  the  front  of  the  apparatus,  and  the  light 
enters  the  instrument  by  means  of  a  comparing-prism,  while  the 
light  radiating  from  the  glowing  substance,  whose  temperature 
is  to  be  measured,  enters  directly.  The  two  intensities  are 
compared  by  means  of  two  Nicol-prisms,  one  of  which  (the 


PYROMETRY  77 

analyzer)  can  be  turned  with  the  eye-piece.  The  angle,  that  can 
be  read  from  a  circular  scale,  serves  as  the  measure  of  intensity, 
while  the  corresponding  temperature  is  read  from  a  table.  If  a 
luminous  body  is  viewed  through  the  apparatus,  the  field  of 
view  appears  divided  into  two  halves  of  unequal  brightness. 
The  eye-piece  is  turned  until  both  parts  show  the  same  bright- 
ness, the  angle  read  and  recorded  and  the  temperature  found 
from  the  table. 

The  entire  apparatus,  whose  optical  parts  are  manufactured 
by  Franz  Schmidt  and  Haenisch  in  Berlin,  is  about  30  cm.  long, 
is  shaped  like  a  telescope  and  is  easy  to  handle.  Three  storage 
batteries  furnish  the  electricity  for  the  little  6- volt  lamp.  Since 
the  light-intensity  of  this  lamp  depends  on  the  e.m.f.  of  the 
storage  batteries,  it  is  necessary  to  adjust  the  lamp  from  time 
to  time  by  means  of  amyl-acetate  lamps. 

On  account  of  the  increasing  weakness  of  light  at  low  tem- 
peratures, 900°  C.  is  taken  as  the  lowest  working  point.  The 
upper  limit  can  be  selected  at  pleasure. 

TABLE   XXII. 

TEMPERATURE-MEASUREMENTS  WITH  THE  WANNER  PYROMETER. 

(a)  In  blast-furnaces. 


Slag. 

Pig  iron 

Pig  iron  from  mixer 

Pig  iron  flowing  into  converter. 
Steel  when  turning  converter. .  . 
Slag  when  turning  converter .  .  . 

Slag,  flowing  out 

Pig  iron,  starting  of  flow 

Pig  iron  in  a  prismatic  form.  .  .  . 

Pig  iron  getting  solid 

Slag  from  mixer 

Slag  from  converter 

Pig  iron  from  blast  furnace 

Steel  from  converter .  : 

Iron  from  cupola 


Deg.  Cent. 

1402  1370 

1317  1284 

1260 

1240 

1460 

1555 

1424  1372 

1384       1372-1330 
1230 
1012 

1384  1330 

1230 
1225 
1211 
1239 


(6)  Thomas-process.  (Temperature  of  converter-gases  during 
charge)  1310°,  1381°,  1472°,  1310°,  1331°,  1472°  and  1494°  C. 
The  temperature  of  the  converter  is  much  higher.  The  tem- 
perature of  the  slag,  three  minutes  after  stopping  the  blower, 
was  found  to  be  1700°  C. 


78 


HEAT  ENERGY  AND  FUELS 


(c)  Various  measurements. 

Zirconium  in  oxygen  gas  blast  2090°  C. 

Electric  arc  light  with  retort  coal  3560-3610°  C. 

Of  other  optical  pyrometers  we  mention  the  apparatus  of 
Holborn-Kurlbaum  and  of  Morse,  in  which  the  intensity  of  the 
electric  standard  lamp  is  varied. 

The  thermo-electric  telescope  of  Fery  (Fig.  18)  is  based  upon 
the  measurement  of  the  total  radiated  energy  of  a  glowing 
substance. 


[^*^f?j^^-:-^=*|SSK 


FIG.  18.  —  Fury's  Thermo-electric  Telescope. 

The  total  radiation  of  energy  of  a  substance  according  to  the 
Stefan-Boltzmann  law  is : 

E  =  K  (T74  -  TV). 

In  this  equation  E  is  the  energy  radiated  from  a  black  body  at 
absolute  temperature  T°  to  a  body  of  the  temperature  T0°  and 
K  is  a  constant.  The  correctness  of  this  law  within  the  widest 
temperature  limits  was  proved  by  Lummer,  Kurlbaum,  Pring- 
sheim,  Paschen  and  others.  The  following  table  gives  the 
observations  of  Pringsheim  and  Lummer: 

TABLE  XXIII. 

RADIATION    OF    ENERGY. 


1 
Black  Body. 

2 

Absolute 
Tempera- 
ture Ob- 
served. 

3 

Reduced 
Deflection. 

4 
K  1010 

5 

Absolute 
Tempera- 
ture Cal- 
culated. 

6 

T  Ob- 
served —  T 
Calculated. 

Boiler  (kettle)  
Saltpetre  kettle  
Do 

373.1 
492.5 
723  0 

156 
638 
3320 

127 
124 
124  8 

374.6 
492.0 
724  3 

Degrees. 
-1.5 
+  0.5 
—  1  3 

Do  
Fire  brick  furnace  
Do  
Do 

745 
810 
868 
1378 

3810 
5150 
6910 
44700 

126.6 
121.6 
123.3 
124  2 

749.1 
806.5 
867.1 
1379 

-4.1 
+  3.5 
+  0.9 
_  i 

Do  ...'... 

1470 

57400 

123  1 

1468 

+  2 

Do  

1497 

60600 

120  9 

1488 

+  9 

Do 

1535 

67800 

122  3 

1531 

+  4 

•  •  >•  • 

Average 

123.8 

PYROMETRY 


79 


The  temperatures  given  in  column  2  are  referred  to  the  tem- 
perature-scale of  Holborn  and  Day,  in  which  the  thermo-electro- 
motive  force  of  the  Le  Chatelier-element  (Pt  +  Platinum  — 
Rhodium)  is  calibrated  with  a  nitrogen-thermometer.  Under 
column  3  we  have  the  radiant  energy  of  the  black  body  at  the 
observed  temperature,  measured  bolometrically  (and  the  gal- 
vanometer-deflection reduced  to  the  same  units).  The  bolometer 
temperature  was  290°  absolute.  The  following  observations  of 
Lummer  and  Kurlbaum  show  the  anomalies  that  have  to  be 
considered  with  other  than  black  bodies.  (See  the  following 
pages.) 

The  radiant  energy  of  ferric  oxide  is  from  4  to  5  times  as  great 
as  that  of  polished  platinum,  but  nevertheless  considerably 
smaller  than  that  of  a  black  body.  With  increasing  temperature 
however  the  radiation  of  non-black  bodies  increases  faster  than 
that  of  absolutely  black  substances. 

In  Fery's  thermo-electric  telescope  (Fig.  18)  the  image  of  the 
glowing  surface  whose  temperature  is  to  be  measured  falls  upon 
the  soldered  joint  of  a  copper  thermo-element,  a  galvanometer 
being  inserted  in  the  circuit  of  the  latter.  The  solder  becomes 
heated,  and  the  thermo-e.m.f.  generated  is  measured  by  the 
galvanometer.  The  image  of  the  glowing  surface  is  thrown  upon 
the  solder  by  means  of  the  eye-piece  0.  The  objective  F  is 
made  of  fluor  spar,  which  absorbs  very  little  of  the  radiant 
energy.  Some  instruments  are  made  with  glass  objectives. 


TABLE   XXIV. 

RADIANT  ENERGY  OF  VARIOUS  SUBSTANCES. 


Absolute  Temperature. 

K              E 

T 

r. 

Black  Body. 

Polished  Plati- 
num. 

Ferric  Oxide. 

372.8 
492 
654 
795 
1103 
1481 
1761 

290.5 
290 
290 
290 
290 
290 
290 

108.9 
109.0 
108.4 
109.9 
109.0 
110.7 

4.23 
5.56 
8.14 
12.18 
16.69 
19.64 

33.1 
36.6 
46  .'9 
64.3 

80 


HEAT  ENERGY  AND  FUELS 


The  following  table  shows  the  close  agreement  of  results, 
determined  with  different  optical  pyrometers,  used  to  measure 
the  temperature  of  the  electric  arc  light.1 

TABLE  XXV. 

COMPARISON    OF    PYROMETRICAL    MEASUREMENTS. 


Observer. 

Absolute  Tempera- 
ture. 

Method. 

Le  Chatelier  ,  .  .  
Violle  

4370 
3870 

Photometry:     intensity    of 
red  light. 
Calorimetry  •     specific    heat 

Wilson  &  Gray  

3600 

of  coal. 
Total  radiation  of  cupric  ox- 

Wanner   

3700-3900**) 

ide  (empirical  equation). 
(According  to  the  coal  used) 

Fery.. 

3600-4000 

photometry;    Wien's  law. 
W^ave   length   of  maximum 

Lummer  &  Prinsrsheim 

3750-4200 

radiation  (Wien's  law), 
do 

Fery  ....    . 

3760**) 

Total     radiation*      Stefan- 

Boltzmann's  law. 

Temperature  of  the  black  body. 


Methods  based  upon  the  change  of  electric  resistance.  Tem- 
perature can  also  be  measured  by  the  change  in  the  electric 
resistance  of  a  spiral  platinum  wire,  wound  around  a  rod  of  fire- 
clay and  protected  from  the  outside  by  a  clay- vessel  (Fig.  19). 


FIG.  19.  —  Spiral  Platinum  Wire  (protected). 

The  law  governing  the  relation  between  resistance  and  tem- 
perature is  represented  by  a  parabola.  This  principle  was  first 
used  by  Siemens,  but  soon  abandoned  in  practice  as  the  plati- 
num is  affected  by  silicon,  phosphorus  and  the  gases  of  reac- 
tion, whereby  its  resistance  is  considerably  changed. 

At  first  a  platinum  tube  was  put  around  the  platinum  wire, 
which  made  the  apparatus  too  fragile  and  too  expensive.  It 
was  soon  found  that  a  porcelain-tube  would  do  just  as  well. 
The  apparatus  therefore  is  very  apt  to  break,  and  is  hardly  used 
except  for  very  accurate  measurements  in  laboratories. 

i  Waidner  &  Burgess:   The  temperature  of  the  arc  (Phys.  Rev.  19,  Nr.  4). 


PYROMETRY 


81 


TABLE  XXVI. 

COMPARISON    OF    PYROMETRICAL    MEASUREMENTS.      (Fischer.) 


Pyrometer  of 


Steinle   &   Hartung 
(Graphite  Pyrometer). 

Siemens   (Resistance 
Pyrometer)  . 

Fischer  (Calori- 
meter) . 

eter  (Geissler). 

Degrees. 
358 

Degrees. 
361 

728 

612 

700 
260 
101 
102 

612 
266 
98 
100 

602 

261 
99.5 
99.8 

103 

99 

99.8 

103 

101 

99  8 

843 

751 

754 

910 
862 

837 

778 

761 

858 

751 

848 

744 

730 

511 

449 

440 

312 

308 

304 

294 

290 

287 

Upon  the  same  principle  are  based  the  pyrometers  of  Hart- 
mann  and  Braun  in  Bockenheim-Frankfurt  am  Main,  of  Callendar 
and  others. 

The  results  of  some  measurements  with  these  instruments 
are  given  in  Table  XXVII: 

TABLE  XXVII. 

MEASUREMENTS   WITH    HARTMANN    AND    BRAUN'S    PYROMETER. 


Deg.  Cent. 


Melting  point: 
Tin 

Bismuth 

Cadmium 

Lead 

Zinc ,  . 

Zinc 

Magnesium,  1%  impurities 

Antimony 

Aluminium,  99 . 5%  Al . .  . . 

Silver 

Gold 

Copper 

K2S04 

K2SO4  solidifying  point. . . 

Na2SO4  melting  point 

Na2SO4  solidifying  point. . . 
Na2CO3,  melting  point. .  .  . 


232  (Callendar  and  Griffiths,  Hey- 

cock  and  Neville) 
270  Callendar  and  Griffiths. 
322  Do. 

329  Do. 

421  Do. 

419  Heycock  and  Neville. 


633 

629.5 

654.5 

960.5 
1062 
1080.5 
1084 
1067 

902 

883 

850 


Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 
Do. 


82 


HEAT  ENERGY  AND  FUELS 


Henri  Le  Chatelier' s  thermo-electric  pyrometer.  This  instru- 
ment is  based  upon  the  measurement  of  the  current 
produced  by  heating  the  soldered  joint  of  a  thermo-element. 
The  solder  immediately  reaches  temperature-equilibrium  with 
the  body  or  space  whose  temperature  is  to  be  measured,  and  the 
instrument  can  be  set  at  quite  a  distance  from  the  place  to  be 
investigated,  which  is  of  considerable  advantage. 

The  selection  of  the  metals  for  the  thermo-element  is  of  impor- 
tance. Iron  or  nickel  cannot  be  used,  as  these  metals,  when 
heated  at  one  point,  set  up  local  currents.  Generally  one  wire 
is  of  platinum  and  the  other  of  platinum  containing  10  per  cent 
of  indium  or  rhodium. 

For  measuring  the  current  Le  Chatelier  uses  a  Deprez 
d'Arsonval  aperiodic  galvanometer  fitted  with  a  mirror  and  scale, 
or  a  needle-galvanometer,  built  according  to  his  instructions 
by  Pellin  in  Paris.  Kaiser  and  Schmidt  in  Berlin  and  Siemens 
and  Halske  use  needle-galvanometers. 

According  to  the  investigations  of  H.  Le  Chatelier  the  relation 
between  the  electromotive  force  and  the  temperature  difference 
between  the  soldered  joint  and  the  extremity  of  an  element 
consisting  of  platinum  and  palladium  can  be  expressed  by  the 
equation :  y  ^ 

e  -  4'3  (t  ~  «  +  1000  (e  -  «• 

He  found      t  -  t0  =  100°    445°      954°     1060°     1550° 
e  -  500  2950  10,900  12,260  24,030 

By  using  a  thermo-element  consisting  of  platinum  and  a  plat- 
alloy,  the  equation  takes  a  different  form. 

TABLE  XXVIII. 
MEASUREMENTS   WITH    THERMO-ELEMENTS. 


Bar  us. 

Le  Chatelier. 

Holborn  and  Wien. 

Pt-Pt  90  +  Ir  10 

Pt  —  Pt  90  +  Rh  10 

Pt  —  Pt  90  +Rh  10 

t 

e 

t 

e 

t 

c 

Degrees. 
300 
500 
700 
900 
1100 

2,800 
5,250 
7,900 
10,050 
13,800 

Degrees. 
100 
357 
445 
665 
1060 
1550 
1780 

550 
2,770 
3,630 
6,180 
10,560 
16,100 
18,200 

Degrees. 
100 
200 
400 
600 
800 
1000 
1200 
1400 
1600 

565 
1,260 
3,030 
4,920 
6,970 
9,080 
11,460 
13,860 
16,220 

PYROMETRY 


83 


All  these  observations  when  plotted  show  similar  curves.  For 
Le  Chatelier's  observation  we  have : 

log  e  =  1.2196  log  t  +  0.302. 

Wherein  e  is  expressed  in  microvolts. 

The  best  way  is  to  calibrate  the  instrument  by  direct  observa- 
tions. For  this  purpose  the  data  given  in  Table  XXIX  can  be 
used- 

TABLE  XXIX. 

DATA    FOR    CALIBRATING    PYROMETERS. 


Boiling  point  of  water 

Boiling  point  of  naphthaline 

Melting  point  of  zinc 

Boiling  point  of  sulphur 

Melting  point  of  aluminium 

Melting  point  of  salt 

Melting  point  of  silicate  of  sodium. 

Boiling  point  of  zinc 

Melting  point  of  silver 

Melting  point  of  gold 

Melting  point  of  palladium 

Melting  point  of  platinum 


Deg.  Cent. 

100 

218 

420 

445 

655  (667) 

800 

883 

930 

960  (961.5) 
1045  (1064) 
1500 
1780 


(The  figures  in  parentheses  were  determined  by  Holborn  and  Wien). 

The  boiling  points  of  water,  naphthaline  and  sulphur  are  de- 
termined by  heating  the  substances  to  the  boiling  point  in  an  in- 
sulated glass  tube  closed  at  the  bottom;  then  the  soldered  joint 
of  the  thermo-element  is  immersed  in  the  vapor.  The  melting 
point  of  zinc  is  observed  by  enclosing  the  thermo-element  in  a 
porcelain  tube  (Fig.  20),  and  immersing  it  in  the  molten  metal. 


i    4 

FIG.  20.  —  Thermo-element  in  Porcelain  Tube. 


FIG.  21.  —  Crucible. 


When  determining  the  melting  point  of  gold  a  few  milligrams  of 
gold  are  placed  under  the  thermo-element,  which  is  put  into  a 
crucible  filled  with  sand  (Fig.  21)  and  heated  above  1000  degrees, 


84 


HEAT   ENERGY  AND   FUELS 


at  the  same  time  carefully  watching  the  movement  of  the  galva- 
nometer. When  the  gold  starts  to  melt,  the  galvanometer  remains 
stationary  until  all  the  gold  is  melted,  when  the  temperature 
continues  to  rise  at  a  steady  rate. 

When  measuring  the  temperature  of  steel-furnaces,  etc.,  the 
thermo-element  must  be  enclosed  in  an  iron  pipe.  For  porcelain- 
furnaces  where  temperature  measurements  are  made  constantly, 
the  thermo-element,  which  is  protected  by  a  glazed  earthenware 
pipe,  is  permanently  attached  to  the  furnace  but  does  not  extend 
into  the  interior  of  the  furnace.  It  is  heated  by  a  specially 
arranged  circular  recess. 

This  instrument  is  made  in  Germany  by  W.  C.  Heraeus  in 
Hanau,  and  by  Kaiser  and  Schmidt  in  Berlin,  as  shown  in  Fig.  22; 


FIG.  22.  —  Holborn-Wien  Pyrometer. 


it  is  specially  constructed  for  industrial  use.  In  the  report  of 
the  "physikalisch-technische  Reichsanstalt,"  the  advantages  of 
the  Holborn-Wien  modification  of  the  Le  Chatelier  pyrometer  are 


PYROMETRY 


85 


set  forth ;  the  reading  of  the  instrument  is  so  simple  that  a  fairly 
intelligent  workingman  can  learn,  in  a  short  time,  how  to  use  it. 
Furthermore  the  instrument  is  durable,  the  accuracy  is  not 
impaired  by  high  temperatures,  the  reading  apparatus  can  be  at 
quite  a  distance  from  the  furnace  and  one  indicating  device  can 
be  used  for  a  number  of  ther mo-elements. 

The  thermo-element  consists  of  a  pure  platinum  wire  0.6  mm. 
in  diameter  and  1500  mm.  long,  one  end  of  which  is  melted  to- 
gether with  the  end  of  another  wire  consisting  of  an  alloy  of  10 
per  cent  rhodium  and  90  per  cent  of  platinum.  The  purity  of 
the  metals  used  is  of  importance  if  the  same  thermo-electromotive 
forces  are  to  be  obtained.  The  opposite  ends  of  the  wire  are  con- 
nected to  a  circuit.  By  heating  the  solder  a  small  e.m.f.  is 
generated  (about  0.001  volt  per  100  degrees  temperature  differ- 
ence between  the  soldered  end  and  the  free  end).  This  e.m.f.  is 
measured  by  means  of  a  galvanometer  provided  with  two  scales, 
one  graduated  in  microvolts,  and  the  other  in  temperature- 
degrees.  According  to  Holborn  and  Wien,  the  accuracy  of  the 
instrument  at  1000°  C.  is  5°  C. 


FIG.  23.  —  Arrangement  of  Element. 

When  in  use  the  wires  of  the  element  must  not  come  in  contact 
with  substances  that  react  with  platinum  or  its  alloys.  This  is 
prevented  by  suitably  mounting  the  instrument  in  a  porcelain- 


86 


HEAT   ENERGY  AND   FUELS 


tube,  which  at  the  same  time  provides  the  insulation  of  the  wires. 
These  porcelain  shells  can  stand  temperatures  up  to  1600  degrees. 
Fig.  23  shows  how  the  element  is  mounted.  A  hard  rubber  disk, 
having  an  opening  in  the  center  is  slid  from  the  bottom  over  the 
outer  porcelain-tube.  This  disk  has  a  recess  which  fits  about  the 
head  B  of  the  porcelain-tube.  A  layer  of  asbestos-cord  is  wound 
in  between  A  and  B.  The  upper  hard  rubber  disk  is  provided 
with  two  small  openings,  through  which  the  wires  of  the  element 
are  drawn  and  a  recess  for  the  porcelain  insulating  tube.  The 
disk  I  is  permanently  connected  with  disk  A  by  means  of  three 
brass  screws.  Two  binding  screws,  which  serve  as  terminals,  are 
attached  to  C.  Asbestos  cord  is  wrapped  around  the  outer 
porcelain-tube,  the  latter  being  forced  into  the  iron  pipe  D.  D 
is  provided  at  the  lower  end  with  a  removable  cap  and  at  the 
upper  end  with  a  bell  E  to  which  the  hard  rubber-head  of  the 
mounted  element  is  fastened  by  means  of  three  iron  screws. 

The  temperatures  of  molten  metals,  slags,  etc.,  are  preferably 
determined  with  floating  pyrometers  of  spheroidal  shape. 

TABLE  XXX. 

TEMPERATURE    DETERMINATIONS,    OPEN-HEARTH    STEEL    FURNACE. 

(Le  Chatelier.) 


Deg.  Cent. 

Gas  leaving  producer 720 

Gas  entering  regenerator 400 

Gas  leaving  regenerator 1200 

Air  leaving  regenerator 1000 

Flue  gases  at  bottom  of  flue 300 

Furnace,  beginning  of  puddling 1550 

Furnace,  end  of  discharge  '. 1420 

Casting-pan,  beginning 1580 

Casting-pan,  end 1490 

GLASS  FURNACE. 

Furnace,  during  refining 1400 

Glass,  during  refining 1310 

Glass,  during  work 1045 

Heating  of  bottles 585 

Rolling  plate-glass 600 

ILLUMINATING  GAS  MANUFACTURE. 

Furnace  on  top 1 190 

Furnace  on  bottom 1060 

Retort  at  end  of  distillation 975 

Flue-gases 680 


PYROMETRY 


87 


The  Hartmann  and  Braun  pyrometer  is  based  upon  the  same 
principle.  The  thermo-elements,  up  to  1000°  C.,  consist  of  plati- 
num and  platinum-nickel,  up  to  1600°  C.  of  platinum  and  plati- 
num-rhodium. The  nickel  element  is  twice  as  sensitive  as  the 
rhodium  element. 

CERAMICS. 

Burning  temperature  of  hard  porcelain 1400°  C. 

Burning  temperature  of  china  porcelain 1275°  C. 

Burning  temperature  of  bricks 1100°  C. 

Wiborgh's  Thermophone  (Fig.  24). 

This  consists  of  a  fire- 
clay cylinder,  containing 
a  small  copper-cartridge 
filled  with  dynamite.  The 
thermophone  is  brought 
into  the  space,  whose  tem- 
perature is  to  be  measured, 
and  the  length  of  time  observed  until  an  explosion  takes  place 
(light  detonation).  The  temperature  is  then  read  from  a  table. 

To  ascertain  the  time  required  for  heating  the  cartridge  by 
heat-conduction  to  the  explosion-temperature  (150°  C.),  Fourier's 
equation  is  used': 


FIG.  24. 


VTZ 

In  this  equation,  t  is  the  outside  temperature;  y,  the  tem- 
perature of  a  point  in  the  interior,  at  a  distance  x  from  the 
surface  after  a  time,  2,  and  6,  the  original  temperature  of  the 
clay-body. 


C  is  the  heat  conductivity  of  the  substance; 

c,  the  specific  heat  of  the  substance; 

d,  the  weight  of  1  cu.m.  of  the  substance,  in  kg.,  and 
z,  time  in  hours; 

x,  the  distance  of  the  point  observed,  from  surface  of  test-body, 
in  meters. 


88  HEAT  ENERGY  AND  FUELS 

Table  XXXI  can  be  used  for  ascertaining  the  temperature. 
TABLE  XXXI. 

DATA  ON  WIBORGH'S  THERMOPHONE. 


I 

II 

I 

ii 

i 

n 

I 

n 

i 

1 
a 

i 

1 

1 

i 

w 
T3 

C 

1 
c 

i 

02 

13 
C 

I 

00 

3 

3 
fi 

i 

rf 

•o 
c 

I 

£3 

i 

t» 

T3 

C 

1 

3 
C 

i 

| 

300 

3 

33  0 

2 

46  4 

1140 

46  2 

36  0 

44  2 

320 
340 
360 
380 
400 

3 
2 
2 
2 
2 

6.0 
45.6 
29.6 
17.0 
6  6 

2 
2 
1 

1 

25.2 
9.2 
56.8 
46.8 
38.6 

1160 
1180 
1200 
1220 
1240 

45.6 
45.2 
44.6 
44.2 
43.8 

35.6 
35.2 
35.0 
34.6 
34.2 

43.6 
43.2 
42.8 
42.4 
42  0 

420 

1 

58  0 

1 

32  0 

1260 

43  4 

33  8 

41  6 

440 
460 
480 
500 
520 
540 
560 

KQfl 

1 
1 

50.6 
44.2 
39.0 
33.8 
30.0 
26.4 
23.0 
20  0 

1 
1 
1 
1 
1 
1 
1 
1 

26.2 
21.4 
17.2 
13.4 
10.2 
7.4 
4.8 
2  4 

1280 
1300 
1320 
1340 
1360 
1380 
1400 
1420 

43.0 
42.6 
42.2 
41.8 
41.4 
41.2 
40.8 
40  4 

33.4 
33.2 
32.8 
32.6 
32.4 
32.2 
32.0 

41.2 
40.8 
40.4 
40.0 
39.6 
39.2 
38.8 
38  6 

fion 

17  2 

1 

0  4 

1440 

40  2 

38  2 

620 

14  8 

58  0 

1460 

39  8 

38  0 

640 
660 
680 
700 

12.6 
10.4 
8.6 

6  8 

56.6 
55.0 
53.6 
52  2 

1480 
1500 
1520 
1540 

39.4 
39.2 
39.0 
38  6 



37.8 
37.4 
37.2 
36  8 

720 

5  2 

50  8 

1560 

38  4 

36  6 

740 
760 

3.6 
2  2 

49.8 
48  6 

1580 
1600 

38.0 
37  8 

36.4 
36  2 

780 
800 
820 

1.0 
59.8 
58  4 

47.6 
46.6 
45  6 

1620 
1640 
1660 

37.6 
37.4 
37  0 



36.0 
35.6 
35  4 

840 

57  4 

44  8 

680 

36.8 

35.2 

SfiO 

KR  4. 

44  0 

1700 

36  6 

35  0 

880 
900 
920 
940 

QfiO 

... 

55.4 
54.4 
53.6 

52.8 

KO  n 

.  .  . 

43.2 
42.6 
41.8 
41.2 

40  fi 

1720 
1740 
1760 
1780 
1800 

..  .. 

36.4 
36.2 
36.0 
35.8 
35  6 

... 

34.8 
34.6 
34.4 
34.2 
34  0 

Q80 

51  2 

40  0 

900 

34.6 

33.0 

1000 
1020 
1040 
1060 
1030 
1100 
1120 

... 

50.6 
49.8 
49.2 
48.6 
48.0 
47.2 
46.8 

39.4 
38.8 
38.2 
37.8 
37.4 
37.0 
36.4 

44.6 

2000 
2100 
2200 
2300 
2400 

33.8 
33.0 
32.2 
31.6 
31.0 

1 

32.2 
31.4 
30.8 
30.2 
29.6 

PYROMETRY  89 

The  thermophone  has  to  be  kept  in  a  dry  place,  and  when  used, 
must  have  an  initial  temperature  of  from  18  to  22°  C. 

(a)  When  determining  the  temperature  in  reverbatory-  or 
muffle-furnaces,  stacks,  etc.,  or  in  all  cases  where  the  thermo- 
phone rests  upon  a  solid  base  and  is  surrounded  by  hot  gases, 
the  time  elapsing  between  the  insertion  of  the  thermophone  and 
the  explosion  is  read  and  the  temperature  taken  from  Table  I. 

(6)  When  determining  the  temperature  of  liquid  metals,  such 
as  zinc,  lead,  copper,  silver  or  gold,  an  iron  pipe,  closed  at  the 
bottom,  30  mm.  inside,  34  to  36  mm.  outside  diameter,  is  inserted 
in  the  molten  metal;  after  a  few  minutes,  when  the  pipe  has 
attained  the  same  temperature  as  the  metal,  the  thermophone  is 
slid  into  the  pipe.  In  this  case  the  temperature  is  read  from 
Table  II. 

(c)  When  measuring  high  temperatures  of  molten  metal  and 
slag,  such  as  iron,  steel,  etc.,  the  thermophone  is  thrown  upon 
the  surface  of  the  metal  and  slag,  and  the  temperature  is  taken 
from  Table  III.  The  above  table  is  made  out  for  0  =  20°  C. 
If  the  air-temperature  differs  from  this  a  correction  must  be  made 
according  to  equation  : 


if  y  =  150°,     6  =  20°, 

we  have: 


If  at  an  air  temperature  of  0'  =  30  degrees  a  temperature  of 
2000  degrees  is  found,  the  correction  is 

— 

=     -142°, 


and  the  measured  temperature  is  t'  =  2000  -  142  -  1858°  C. 

The  results  obtained  with  the  thermophone  are  very  satis- 
factory. Contact  of  the  thermophone  with  basic  slags  has  to  be 
avoided,  since  in  such  cases  the  explosion  takes  place  too  early, 
which  gives  too  high  results. 


90 


HEAT   ENERGY  AND   FUELS 


TABLE   XXXII. 
COMPARATIVE    DATA    ON    WIBORGH'S    THERMOPHONE. 


Temperature-  Measurements. 

Air  Pyrometer. 

Thermophorie. 

Heating  furnace 

784  5 

Deg.  Cent. 
772     764 

Heating 

875.0 

888     878 

Open-hearth  steel  upon  acid  slag.  .  . 
upon  steel                                

over  2400 
1812 

upon  strongly  basic  slag 

over  2400 

In  practice  automatic  registering  pyrometers  are  very  useful 
as  they  make  a  continuous  control  of  the  temperature-changes 
possible.  Because  of  lack  of  space  they  cannot  be  described  in 
this  book. 

Suggestions  for  Lessons. 

Practice  in  handling  various  pyrometers; 
Adjustment  of  same; 

Determination  of  melting  points,  heating  and  cooling  curves; 
Comparative  temperature-measurements  with  different  pyro- 
meters. 


CHAPTER  IV. 
COMBUSTION  HEAT  AND  ITS  DETERMINATION. 

HEAT  value,  fuel  value,  thermal  value,  calorific  value  or  ther- 
mal efficiency  is  the  quantity  of  heat  developed  from  a  certain 
quantity  of  fuel  in  complete  combustion.  It  is  generally 
expressed  in  calories. 

This  quantity  is  called  absolute  thermal  value,  etc.,  if  it  is 
referred  to  the  unit  of  weights,  specific  thermal  value,  if  referred 
to  the  unit  of  volume. 

Pyrometric  thermal  efficiency  is  called  the  temperature  that 
can  theoretically  be  reached  by  combustion  of  the  fuel. 

We  are  going  to  speak  first  of  the  absolute  thermal  value  or, 
chemically  expressed,  of  the  determination  of  the  combustion- 
heat,  which  is  generally  figured  in  calories,  sometimes  however 
given  in  per  cents  of  the  thermal  value  of  pure  carbon,  or  as 
"evaporating-power,"  or  in  comparison  with  some  other  fuels, 
or  as  the  quantity  of  lead  reduced  by  1  g.  of  fuel. 

The  expression  of  the  thermal  value  in  calories  is  easily  under- 
stood as  it  means  the  number  of  large  calories  furnished  by  the 
combustion  of  1  kg.  of  fuel.  If  this  quantity  is  divided  by  8080 
(the  thermal  value  of  1  kg.  of  charcoal  according  to  Favre  and 
Silbermann)  the  thermal  value  is  obtained,  expressed  in  terms 
of  the  heat- value  of  pure  carbon. 

The  expression  of  the  thermal  value  of  a  fuel  by  its  "  evapo- 
rating power"  was  first  proposed  by  Karmarsch.  It  means  the 
quantity  of  water  transformed  into  steam  by  1  kg.  of  fuel  and  is 
obtained  by  dividing  the  thermal  value  expressed  in  calories 
with  652  (the  heat-quantity,  necessary,  according  to  Regnault, 
to  transform  1  kg.  of  water  at  0°  C.  into  steam  at  150°  C.). 

For  certain  purposes  the  thermal  value  of  one  fuel  is  compared 
with  the  value  of  another  fuel,  i.e.  the  fuel  quantity  equivalent 
to  the  other  is  given.  Generally  1  cubic  meter  of  soft  logwood 
.is  taken  as  unity  which  has  a  thermal  value  of  about  900,000  cal. 

Table  XXXIII  will  be  useful  for  transformations. 

91 


92 


HEAT  ENERGY  AND   FUELS 


TABLE   XXXIII. 

THERMAL    TRANSFORMATION    VALUES. 


Thermal  Value  in 

Calories 

Referred  to  1  Kg.  of 

Evaporating  Power. 

Logwood. 

Pure  Carbon. 

1 

0.00012376 

0.0015337 

0.000001111 

8080 

1 

12.39 

0.00898 

652 

0.080693 

1 

0.000724 

900.000 

111.4 

1380 

1 

In  determining  the  thermal  value  account  has  to  be  taken  of 
the  quantity  of  hydrogen  present  which  is  oxidized  to  water. 
According  as  we  assume  that  this  water  is  completely  condensed 
or  completely  changed  to  steam ,  we  obtain  the  highest  and 
lowest  calorific  values,  respectively. 

The  following  methods  have  been  proposed  for  determining 
the  fuel  value : 

1.  Direct  determination  of  the  thermal  value. 

(a)  On  a  small  scale,  in  calorimeters. 
(6)  On  a  large  scale,  in  steam-boilers. 

2.  By  means  of  empirical  formula  based  on  certain  chemical 
tests. 

(a)  Calculation  of  the  thermal  value  from  the  chemical 
composition  (elementary  analysis). 

(6)  Calculation  of  the  thermal  value  from  the  quantity  of 
oxygen  required  for  complete  combustion  (Berthier's  method). 

(c)  Based  on  simple  chemical  tests. 

(1)  Direct  determination  of  the  thermal  value.  These  methods 
undoubtedly  give  the  best  results.  Several  details  have  to  be 
considered;  all  losses  or  gains  of  heat  have  to  be  avoided.  This 
is  easier  accomplished  in  small  than  in  large  apparatus. 

The  determination  of  the  thermal  value  on  a  small  scale,  how- 
ever, has  a  disadvantage  in  that  it  is  very  difficult  to  get  a  good 
average  sample  small  enough  to  be  burned  in  a  small  apparatus. 
The  only  apparatus  to  be  recommended  are  those  in  which  a 
single  reliable  determination  can  be  made  simply  and  quickly, 


COMBUSTION  HEAT  AND  ITS  DETERMINATION 


93 


so  that  a  great  number  of  determinations  can  be  made  on  any 
one  sample  without  difficulty. 

We  shall  consider  here  only  some  of  the  most  widely  used 
calorimeters. 

Of  the  calorimeters  in  which  combustion  with  oxygen  under 
atmospheric  pressure  takes  place  we  shall  describe  only  the 
calorimeter  of  F.  Fischer  (Fig.  25). 
The  oxygen  for  combustion  is  led 
(sometimes  after  being  washed  with 
caustic  potash  and  dried)  through 
the  gas  pipe  a  and  the  platinum 
pipe  r.  The  latter  is  fitted  loosely 
in  the  cover  e  of  the  combustion- 
chamber  A  (made  of  95  per  cent 
silver)  and  reaches  into  the  platinum- 
crucible  t,  which  contains  about  1  g. 
of  the  fuel  to  be  tested.  The  com- 
bustion gases  escape  through  the 
platinum-net  u  and  then  upwards 
between  crucible  and  ring  V  through 
s,  i  and  e  into  the  pipes  c  and  6.  The 
platinum-net  u,  upon  which  some 
soot  is  deposited,  finally  gets  so 
hot  that  the  soot  is  burned.  The 
calorimeter- vessel  B,  which  contains 
1500  g.  of  water,  is  surrounded  by 
a  layer  of  mineral  wool  C  and  the 
wooden  case  D.  The  two  thermo- 
meters t  serve  for  measuring  the 
temperature  of  the  calorimeter 
water  and  of  the  escaping  gases 
respectively ;  w  is  a  stirrer,  operated 

,     ,         .„  FIG.  25.  —  Fischer's  Calorimeter. 

by  m  and  the  silk-cord  o.    By  means 

of  a  magnifying  glass  one  one-hundredth  of  a  degree  can  be 

observed  and  recorded. 

Calorimeters  in  which  combustion  in  oxygen  takes  place  under 
pressure,  as  for  instance  the  apparatus  of  Berthelot,  Mahler, 
Stohman,  etc.,  are  very  convenient.  In  all  these  methods  the 
combustion  of  the  fuel  takes  place  in  a  closed  chamber,  in  which 
the  fuel  is  enclosed  with  a  sufficient  amount  of  compressed 


94 


HEAT  ENERGY  AND  FUELS 


oxygen.  The  increase  of  temperature  of  a  certain  mass  of  water 
(calorimeter-water)  into  which  the  apparatus  is  immersed,  is 
observed  and  recorded. 

The  calorimetric  bomb  of  Mahler  is  illustrated  in  Fig.  26  and 
consists  of  the  following  parts:  (1)  A  bomb  B  made  of  excel- 
lent steel  somewhat  softer  than  gun-steel.  This  steel  has  an 


FIG.  26.  —  Calorimeter  Bomb  (Mahler). 

absolute  strength  of  55  kg.  per  sq.  mm.  and  22  per  cent  elonga- 
tion. The  quality  of  the  steel  was  carefully  selected  on  account 
of  the  strength  and  also  on  account  of  the  enameling,  of  which 
we  will  speak  later. 

The  bomb  has  a  capacity  of  654  cu.  cm.  and  its  walls  are  8  mm. 
thick.  This  capacity  is  much  larger  than  that  of  Berthelot's 
bomb,  the  object  being  to  obtain  ari  oxygen  surplus  even  when 
using  a  gas  not  entirely  pure.  Fuel-gases  are  also  studied  with 
this  bomb.  The  fuel  gases  often  contain  as  much  as  70  per  cent 
of  inactive  substances,  which  make  it  necessary  to  take  con- 
siderable quantities  when  testing  in  order  to  obtain  a  measurable 
increase  of  temperature  in  the  calorimeter. 

The  oval  shape  was  selected  in  order  to  facilitate  the  forging 
and  enameling.  The  bomb  is  nickel-plated  on  the  outside,  and 
coated  with  enamel  on  the  inside  to  prevent  any  bad  effects  from 
nitric  acid,  which  is  always  formed  by  combustion.  This  enamel 
takes  the  place  of  the  platinum-lining  in  Berthelot's  apparatus. 

The  bomb  is  closed  with  a  threaded  plug  packed  with  sheet 
lead.  The  plug  is  provided  with  a  taper  threaded  cock,  which 


COMBUSTION  HEAT  AND   ITS  DETERMINATION  95 

serves  as  inlet  for  the  oxygen  and  through  which  is  inserted  a 
well  insulated  electrode  E,  which  is  attached  to  a  platinum 
rod  F  that  extends  towards  the  interior.  Another  platinum 
rod,  also  fastened  to  the  plug,  carries  a  platinum  cap  for  receiving 
the  fuel  to  be  tested. 

(2)  The  other  parts  of  the  apparatus  are  the  calorimeter  D, 
the  calorimeter- jacket  A  and  the  stirrer  S.     They  differ  in  details 
from  Berthelot's  apparatus  and  are  less  expensive. 

The  spiral-shaped  stirrer  of  Berthelot  is  replaced  here  by  a 
simple  and  easily  operated  circulation  device  which  allows  the 
production  of  a  uniform  circulation. 

(3)  We   may  further   mention:    the  thermometer,  which  is 
divided  in  T£o  degree,  the  source  of  electricity  P  and  a  watch  or 
minute-glass. 

(4)  Mahler  uses  oxygen  from  an  oxygen-bomb.      Since  the 
most  favorable  pressure  for  burning  1  g.  of  bituminous  coal  is 
about  25  atm.,  and  since  the  bombs  contain   1200  liters  (120 
atm.),  one  of  these  vessels  is  sufficient  for  about  100  determi- 
nations.    A  pressure-gauge  (manometer)  inserted  between  the 
oxygen-bomb  and  calorimeter-bomb  allows  the  pressure  of  the 
oxygen  to  be  controlled. 

The  pressure  used  with  solid  and  liquid  fuels  is  25  atm. ;  with 
gases  rich  in  carbon  (illuminating  gas,  etc.)  5  atm.,  and  with 
poor  gases  (producer  gas,  etc.)  1  atm.  To  insure  the  complete 
combustion  a  certain  excess  of  oxygen  must  be  present;  too 
great  an  excess,  however,  would  lower  the  combustion  tempera- 
ture and  thereby  cause  incomplete  combustion. 

The  two  insulated  electric  conductors  which  pass  through 
the  plug  are  connected  inside  the  bomb  by  a  spiral  made  of 
0.1  mm.  iron- wire,  that  extends  into  the  fuel  and  causes  ignition 
after  the  state  of  incandescence  is  reached. 

The  fuel  is  contained  in  a  small  vessel  of  platinum,  which  is 
connected  in  the  electric  circuit.  In  a  bomb  containing  650 
cu.  cm.,  1  g.  of  fuel  is  used.  Slightly  volatile  liquids  can  also  be 
used  directly. 

When  measuring  gases  the  bomb  is  evacuated  and  filled  with 
gas  at  certain  temperature  under  pressure,  which  process  is 
repeated  twice  for  removing  every  trace  of  air. 

It  is  necessary  that  the  calorimeter- water  and  jacket  water  be 
in  temperature-equilibrium  with  the  air  of  the  room.  All  the 


96  HEAT   ENERGY   AND   FUELS 

apparatus  is  allowed  to  stand  in  the  test  room  for  24  hours  pre- 
vious to  the  test,  immersed  in  a  sufficient  amount  of  water.  The 
apparatus  has  to  be  protected  from  the  sun  and  from  draughts, 
which  will  cause  a  variation  of  temperature. 

The  constants  of  the  calorimeter  are  determined  by  burning 
a  known  quantity  of  a  certain  substance  of  known  thermal  value, 
for  instance,  1  g.  of  naphthaline  yielding  0.70  cal. 

When  making  a  determination,  1  g.  of  the  powdered  fuel  is 
weighed  and  put  into  the  small  vessel.  The  powder  should  not 
be  too  fine,  as  otherwise  it  might  be  carried  away  by  the  current 
of  oxygen.  If  a  fine  powder  is  to  be  used  it  is  wrapped  up  in 
paper  of  known  weight  and  known  thermal  value. 

The  bomb  is  closed  and  the  oxygen  allowed  to  enter  slowly  so 
as  to  avoid  blowing  away  the  powder.  When  the  desired  pressure 
is  reached  the  cock  is  closed  and  the  bomb  cut  off  from  the  manom- 
eter. The  bomb  is  put  into  the  calorimeter,  five  minutes  being 
allowed  for  equalizing  the  temperature.  The  vessel  must  be  held 
upright  to  avoid  spilling  the  powder.  The  stirrer  is  moved  rap- 
idly and  continuously  for  three  minutes  in  order  to  obtain  a  uni- 
form temperature  of  the  water,  and  the  temperature  of  the 
calorimeter  read  and  recorded. 

The  fuel  is  ignited  by  impressing  10  volts  on  an  iron- wire;  the 
temperature  is  read  and  recorded  every  minute  for  six  minutes. 
The  temperature  equilibrium  of  the  bomb  and  calorimeter  is 
generally  perfect  after  three  minutes.  The  readings  during  the 
next  three  minutes  are  used  to  correct  the  heat  lost  by  radiation. 

It  is  generally  sufficient  to  add  to  the  increase  of  temperature 
recorded  three  minutes  after  ignition  the  decrease  of  temperature 
observed  during  the  two  following  minutes.  This  is  not  abso- 
lutely correct,  but  sufficiently  so  for  commercial  purposes.  The 
exact  corrections  give  results  varying  not  more  than  ^^  from  the 
correction  mentioned. 

A  second  correction  relates  to  the  combustion  heat  of  the  iron- 
wire  in  oxygen,  which  amounts  to  1.600  cal.  per  1  g.  iron,  and  to 
the  heat  liberated  by  the  formation  of  a  small  quantity  of  nitric 
acid.  The  latter  quantity  has  to  be  determined  for  very  accurate 
work,  but  can  be  neglected  in  commercial  tests,  the  error  amount- 
ing to  less  than  -3^  and  being  nearly  compensated  by  the  error 
in  the  correction  for  cooling.  1  g.  HN03  yields  by  its  forma- 
tion 0.230  cal. 


COMBUSTION  HEAT  AND  ITS  DETERMINATION 


97 


EXAMPLE  :  One  g.  of  naphthaline  is  used  for  combustion. 

Water-content  of  calorimeter 2200  g. 

Water-value  of  bomb,  etc 480  g. 

Total 


2680  g. 


Measurements  of  temperature : 


Before  Test. 

Combustion. 

Cooling. 

0'      17.52° 
1'      17.52° 
2'      17.52° 

3'      20.15 
4'      21.06 
5'      21.11 

6'      21.09° 
1'     21.07° 
8'     21.09° 

Rise  in  temperature  observed 3.59° 

Correction  for  cooling 0.04° 

Total  ~3£3° 

Quantity  of  heat,     3.63    X  2.68  -  9.728  cal. 

Correction  for  iron,  0.025  X  1.60  =  0.040  cal. 

Difference  9.688  cal. 

If  a  correction  for  the  nitric  acid  formed  had  been  made  the 
result  would  have  been  9.685  cal. 

Mahler  found  in  a  lecture,  i.e.  under  conditions  which  pro- 
hibited the  attainment  of  temperature-equilibrium  in  the  calorim- 
eter, 8373  cal.  as  the  fuel-value  of  a  bituminous  coal,  while  in 
the  laboratory,  when  taking  all  precautions,  he  obtained  a  value 
1.3  per  cent  lower. 

If  the  coal  contains  considerable  amounts  of  sulphur,  same  has 
to  be  considered.  The  sulphur  is  completely  oxidized  to  sulphuric 
acid  and  can  be  determined  by  well-known  methods  after  washing 
the  bomb  with  water.  The  other  calorimeter-bomb,  in  which 
combustion  is  effected  with  oxygen  under  pressure,  is  arranged 
in  a  somewhat  similar  manner. 

All  determinations  made  in  such  apparatus  have  two  defects. 
They  give  a  thermal  value  at  constant  volume  while  in  practice 
all  combustion  takes  place  at  constant  pressure;  on  the  other 
hand  they  give  the  so-called  upper  thermal  value,  as  the  hygro- 
scopic water  of  the  coal,  and  the  coal  formed  by  combustion  is 
cooled  to  air-temperature,  i.e.  condensed,  so  that  the  thermal 
value  determined  in  the  bomb  includes  the  latent  heat  of  evapora- 


98 


HEAT   ENERGY  AND  FUELS 


2440  g. 


tion  of  the  water,  which  can  never  be  utilized  in  firing.  To 
counteract  this  last  defect  Krocker  proposes  to  put  the  bomb 
after  combustion  into  an  oil- bath  at  from  105°  to  110°  C.,  arid 
to  absorb  the  evaporated  water  in  a  calcium  chloride  appa- 
ratus ;  finally,  to  pass  dry  air  through  the  bomb.  Since  he  uses 
very  exact  corrections  for  the  cooling  of  the  calorimeter,  we 
give  an  example  of  his  method. 
Temperature  of  the  room  20  degrees. 

Water  in  calorimeter  =  2100  g. 

Water  value  of  the  apparatus  340  g. 

Weight  of  iron- wire  and  coal-brickette  =  1.0959  g. 
Weight  of  iron-wire  alone  =  0.0187  g. 

Weight  of  coal-brickette  alone  —  1.0772  g. 

Weight  of  the  chloride  of  calcium  apparatus : 

(a)  Before  test 48.2169  g. 

(b)  After  test 48.7605  g. 

Weight  of  total  water 0.5436  g. 

Weight  of  water  in  02 0.0250  g. 

Weight  of  water  in  coal 0.5186  g.  =  48% 

TABLE   XXXIV. 

TEMPERATURE   CHANGE. 


First 

Test. 

Main 

Test. 

After  1 

'eat. 

No. 

Reading. 

Differ- 
ence. 

Reading. 

Differ- 
ence. 

Reading. 

Differ- 
ence. 

Note. 

r  = 

»«• 

t  = 

t=* 

T'  = 

v'  = 

1 

18.750 

+ 

18.759 

18.759 

21.744 

_ 

The     coal 

2 

18.753 

0.003 

19.170 

21.742 

0.002 

was  burned 

3 

18.753 

0.000 

20.530 

21.739 

0.003 

as   furnish- 

4 

18.756 

0.003 

21.240 

21.729 

0.010 

ed   without 

5 

18.756 

0.000 

21.590 

21.720 

0.009 

being  made 

6 

18.757 

0.001 

21.723 

21.713 

0.007 

air  dry. 

7 

18.758 

0.001 

21.749 

21.749 

21.707 

0.006 

g 

18   7^8 

0   flOfl 

01    7fl4 

0  003 

g 

18  759 

0  001 

2  990 

10 

18.759 

0.000 

jm 

187.759 

0.009 

173.798 

0.040 

ver. 

18.756 

0.001 

21.725 

0.005 

COMBUSTION  HEAT  AND  ITS  DETERMINATION  99 

The  temperature  of  the  calorimeter  water  rose  2.990°  C. 
For  correcting  the  temperature  the  formula  of  Regnault-Stoh- 
mann-Pfauneller  is  used : 


+ 


7{  \ 

W    -  nr  j-  (n  -  l)v. 


v  means  herein  average  of  temperature-differences  of  the 
preliminary  test. 

T  means  herein  average  of  temperature-readings  of  the  pre- 
liminary test. 

tv  t2 .  .  tn  means  herein  the  temperature-readings  of  the  main 
test. 

v'  means  herein  average  of  temperature-differences  of  final 
test. 

T'  means  herein  average  of  temperature-readings  of  final  test. 

n  means  herein  number  of  readings  of  main  test. 

For  our  example  we  have : 

v  -  v'  =    0.001   +   0.005  =.0.006° 
T'  -  T  =  21.725  -  18.756  =  2.969° 


*.  +  <»_  40.488  _2Q011o 
2  2 

n-l 

£    (t)  =  123.002° 

i 

nr  =  1  x  18.756  -  131.292° 
(n  -  1)  v  =  6  X  0.001  -  0.006°. 

The  correction  therefore  is : 

0  006 
Corr-  =  <    ^  (°-046  +  20-244.  +  123.012  -  131.292)  -  0.006 


=  0.012°. 

Corrected  increase  of  temperature  =  2.990  -f  0.012  =  3.002°. 
Heat  generated  in  calorimeter 

3.002  X  2440  =  7324.8  cal. 


100  HEAT  ENERGY   AND   FUELS 

If  we  deduct  herefrom  2.92  cal.  (that  are  developed  from 
0.0187  g.  iron-wire  in  combustion)  we  get  the  thermal  value 
of  the  coal: 

7324.8  -  29.9 


1.0772 


=  6772  cal. 


For  the  acids  formed  Krocker  deducts  8  cal.  (as  average),  whereby 
the  thermal  value  of  the  coal  becomes : 

7324.8  -  29.9  -  8 
-T0772- 

Altogether  0.5436  g.  of  water  were  absorbed  by  the  calcium 
chloride.  According  to  previous  tests  0.025  g.  of  same  come 
from  the  compressed  oxygen,  so  that  for  the  coal  burned  we 
have  0.5436  -  0.025  g.  -  0.5186  g.  of  water  (48  per  cent  of  the 
coal  burned).  The  latent  heat  of  evaporation  is: 

0.48  X  600  -  288  cal. 

so  that  we  get  as  useful  thermal  value  of  the  coal  (lower  heat- 
value) 

6764  -  288  =  6476  cal. 

Since  the  quantity  of  hygroscopic  water  in  coal  varies  widely, 
only  dried  coal  should  be  used  for  the  determination  of  fuel 
values.  Furthermore  since  the  determination  of  the  water 
content  of  the  calorimeter  is  a  tedious  operation,  it  is  of  advan- 
tage to  determine  the  hydrogen  content  of  coal  by  elementary 
analysis. 

A  calorimeter  constructed  by  S.  W.  Parr,  professor  in  the  State 
University  at  Champaign,  111.,  for  determinating  fuel  values  is 
more  and  more  widely  used  on  account  of  its  low  cost.  This 
calorimeter  is  based  upon  the  same  principle  as  the  calorimeter- 
bombs,  i.e.  the  combustion  takes  place  in  an  enclosed  space,  so 
that  during  the  process  no  gases  can  enter  or  escape.  The  oxygen 
is  used  in  solid  form  and  the  products  of  combustion  obtained 
are  transformed  into  solid  compounds,  therefore  combustion 
takes  place  at  low  pressure,  and  the  expensive  bomb  is  done  away 
with. 


COMBUSTION  HEAT  AND  ITS  DETERMINATION 


101 


Fig.  27  shows  the  assembled  apparatus,  Fig.  28  the  reaction- 
vessel  (the  cartridge).  The  calorimeter  proper  consists  of  a 
nickel-plated  copper- vessel  A,  which  contains  somewhat  over 
2  liters  and  a  vessel  (7,  made  of  wood  fiber  and  surrounded  by 


if 


FIG.  27.  —  Parr  Calorimeter. 


FIG.  28.  —  Reaction  Vessel  (for  27). 


another  similar  vessel,  B.  The  entire  apparatus  is  closed  by 
the  double-cover  G,  made  of  one  piece.  Thereby  such  an  excel- 
lent heat-insulation  is  effected  that  the  maximum  temperature 
attained  in  the  reaction  remains  constant  for  five  minutes, 
without  falling  even  0.001°. 

The  reaction  vessel  D  is  a  heavy,  nickel-plated,  brass  cylinder 
having  a  cubic  content  of  about  35  cu.  cm. ;  it  is  closed  at  top  and 
bottom  with  screw  plugs  and  leather  gaskets.  The  lower  plug, 
I,  rests  upon  a  pivot-step  bearing,  F,  connected  to  the  cylinder 
E.  The  upper  plug  is  provided  with  a  tube  H,  which  extends 
through  the  cover,  G,  and  carries  the  pulley,  P.  The  four  blades, 
h,  h,  are  attached  to  D.  If  the  device  is  set  in  motion  (by  mean's 
of  a  Raabe-turbine)  at  sufficiently  high  speed  (150  rev.  per  min.) 
the  calorimeter-water  moves  in  the  direction  of  the  arrows  and  a 
perfectly  uniform  temperature  distribution  is  obtained  in  the 
calorimeter. 

From  Fig.  28,  which  shows  the  reaction  vessel  (cartridge)  on 
a  larger  scale  it  can  be  seen  that  the  tube  H  contains  a  small 


102  HEAT   ENERGY   AND   FUELS 

tube  L  which  is  open  at  one  side  and  ends  at  the  bottom  in  a 
conical  valve  K.  The  latter  is  kept  closed  by  the  spiral  spring 
M  until  pressure  is  applied  to  N. 

In  the  cover,  G,  a  hole  (8-9  mm.  wide)  is  provided,  through 
which  a  thermometer  divided  at  least  in  ^o  degrees,  but  better  in 
T£o  degrees,  is  suspended.  The  scale  of  the  thermometer  goes 
from  15  to  26  degrees  and  is  38  to  40  cm.  long.  It  is  of  impor- 
tance to  have  the  graduated  part  of  the  thermometer  absolutely 
and  perfectly  cylindrical. 

The  manipulation  of  the  instrument  is  as  follows:  After 
putting  the  double- vessel,  CB,  upon  a  solid  table  the  calorimeter- 
vessel,  A,  is  filled  outside  of  the  wooden  jacket  with  exactly  2 
liters  of  water  (preferably  distilled  water),  care  being  taken  to 
keep  the  outside  of  A  and  the  inside  of  C  dry.  The  temperature 
of  the  water  should  be  about  2  degrees  below  the  temperature  of 
the  room.  A  is  now  put  into  the  wooden  vessel,  CB,  the  reaction- 
vessel,  D,  is  dried  perfectly  by  slightly  heating  on  the  sand-bath, 
the  lower  cover,  7,  is  tightly  screwed  on  and  about  10  g.  of  per- 
oxide of  sodium  (sifted  through  1  mm.  mesh)  put  in.  Next 
0.5  or  1  g.  of  the  fuel  and  other  substances,  to  be  mentioned  later, 
are  introduced  into  the  reaction-vessel,  and  the  cover  (whose 
valve  if  it  should  have  gotten  wet,  has  to  be  dried)  put  on. 
While  pressing  N  upwards,  the  charge  is  well  shaken,  then 
lightly  tapped  to  settle  the  mass  on  the  bottom,  the  valve  K 
tried  to  see  if  it  works  easily,  hh  attached  and  vessel  D  inserted 
in  A.  The  cover,  G,  is  now  put  on,  also  pulley,  E,  and  the  cord 
put  over  the  latter,  then  the  thermometer,  r,  is  arranged  as  shown 
in  the  figure.  The  stirrer  is  operated  (about  3  minutes)  until 
the  thermometer  reading  is  perfectly  constant,  the  reading 
recorded  but  the  motor  kept  going  to  the  end  of  the  test. 

Ignition  is  effected  by  means  of  a  glowing  piece  of  iron  wire 
10  mm.  in  length  and  2.5  mm.  in  diameter,  weighing  about 
0.4  g.  Such  a  piece  can  be  used  frequently  until  its  weight  is 
considerably  less  than  0.4  g.  At  a  temperature  of  700  degrees 
this  wire  carries  0.4  X  0.12  X  700  =  33.6  cai.,  which  corresponds 
to  an  increase  of  temperature  of  0.016  degrees  in  the  calorimeter. 
As  readings  are  made  with  an  exactness  of  0.005  degree,  correc- 
tion is  made  by  subtracting  from  the  temperature  recorded  0.015 
degree.  The  iron  wire  is  seized  by  means  of  curved  tweezers, 
heated  to  red  glow  in  a  Bunsen  flame,  allowed  to  fall  through  N 


COMBUSTION  HEAT  AND  ITS  DETERMINATION         103 

into  the  reaction-vessel ;  then  N  is  pressed  down  with  the  tweezers 
and  quickly  released,  so  that  the  iron  falls  out  of  K  without  any 
gas  escaping  at  L.  A  noise  is  heard  for  several  seconds,  and  the 
temperature  rises  first  rapidly  then  slowly.  After  4  or  5  minutes 
the  maximum  is  reached,  which  remains  constant  for  about  5 
minutes,  then  the  reading  is  recorded.  The  test  now  being 
finished,  the  motor  is  stopped  and  the  apparatus  taken  apart. 
Cylinder,  D,  is  put  into  a  dish  filled  with  warm  water,  wherein 
its  contents  are  dissolved  accompanied  by  the  generation  of 
heat.  After  neutralizing  the  solution  with  hydrochloric  acid 
it  is  easily  noticed  whether  unburned  particles  of  coal  are 
present,  in  which  case  the  test  is  unsuccessful.  This,  however, 
happens  only  with  anthracite,  when  persulphate  of  potash  has 
not  been  added.  With  bituminous  coal  an  addition  of  tartaric 
acid  is  sufficient,  while  with  lignite  simply  double  the  amount  of 
coal  is  used,  without  the  addition  of  anything.  Vessel,  D,  is 
immediately  washed  and  dried. 

The  water-value  of  the  calorimeter  is  123.5  g.  (which  should 
be  checked) ;  we  have  therefore,  including  the  calorimeter-water, 
2123.5  g.  According  to  numerous  tests  (with  an  increase  of 
temperature  =  t'  -  t)  73  per  cent  of  the  heat  generated  is  from 
the  combustion  proper,  27  per  cent  from  the  reaction  of  the 
products  of  combustion  .  with  Na20  and  Na202  respectively. 
If  1  g.  of  coal  has  been  burned  (lignite),  0.73  X  2123.5  (If  -  t) 
=  1550  (t'  —  t)  cal.  are  generated.  We  have  therefore  simply 
to  deduct  0.015  degree  (for  the  heat  introduced  with  the  hot 
iron-wire)  from  the  recorded  difference  of  temperatures  t'  —  t 
and  to  multiply  the  quantity  obtained  -by  1550,  to  get  the 
thermal-value  of  1  g.  of  coal. 

With  bituminous  coals,  of  which  0.5  g.  is  used,  the  difference 
of  temperature  recorded  would  have  to  be  multiplied  by  3100. 
Previously  however  0.85  degree  has  to  be  deducted  for  0.5  g.  of 
tartaric  acid  and  0.4  g.  of  iron  at  700  degrees. 

With  anthracite  the  following  points  have  to  be  observed: 
1.0  g.  of  persulphate  and  0.4  g.  of  iron  effect  an  increase  of 
temperature  of  0.155  degree;  on  the  other  hand,  0.5  g.  of  tartaric 
acid  and  0.4  g.  of  iron  effect,  as  we  have  seen  above,  an  increase 
of  0.85.  Since  only  one  piece  of  iron  is  used  for  ignition  we  have 
to  deduct  the  corresponding  increase  of  temperature  and  we 
therefore  have  as  correction  for  0.5  g.  tartaric  acid,  1.0  g.  of 


104 


HEAT  ENERGY  AND  FUELS 


persulphate  and  0.4  g.  of  iron,  0.85  +  0.155  -  0.015  =  0.99 
degree. 

If  the  sodium  peroxide  is  too  moist,  the  results  obtained  are 
too  high;  in  such  a  case  a  second  test  is  made  with  0.5  g.  of 
tartaric  acid  and  about  7  g.  of  sodium  peroxide.  If  now  the 
temperature  of  the  calorimeter  increases  more  than  0.85  degree, 
this  has  to  be  considered  in  the  main  test  by  deducting  0.15 
degree  for  every  0.1  degree  of  observed  additional  increase. 
This  correction  however  can  be  avoided  if  the  peroxide  is  kept 
in  air-tight  cans  of  50  g.  or  100  g.  capacity. 

Care  must  be  taken  not  to  throw  the  mixture  of  coal  and 
peroxide  into  water,  as  otherwise  an  explosion  might  take  place. 
This  is  also  the  reason  why  the  interior  of  the  valve  has  to  be 
kept  absolutely  dry. 

Parallel  tests  made  by  Lunge  and  Parr  with  Parr's  calorimeter 
and  Mahler's  bomb  gave  the  results  shown  in  Table  XXXV. 


TABLE   XXXV. 
TESTS  WITH  PARR'S  CALORIMETER. 


Kind  of  Coal. 

Water. 

Ash. 

Thermal  Value. 

Differ- 
ence. 

Additions. 

Mah- 
ler. 

Parr. 

Ruhr  flaming 
coal    ...... 

2.6 

7.1 

7685 

7688  )  ?695 
7703  (  7' 

+  10 

0.600  g.  Tartaric  acid 

Ruhr  coal.  .  .  . 

1.3 

6.6 

8059 

8075 

-f  16 

0.5  g.  Tartaric  acid 
1.000  g.  Persulphate 

Anthracite... 

1.5 

6.7 

7981 

7967  )  7Q90 
8013  \  7" 

+    9 

0.600  g.  Tartaric  acid 

Coke......... 

0.6 

13.0 

6640 

6649  )  fiftfi7 
6726  \  6687 

+  47 

0.500  g.  Tartaric  acid 

Welsh 
Anthracite.  . 

2.0 

4.2 

8049 

8044  )  8Q21 
7998  \  8021 

-28 

0.  600  g.  Tartaric  acid 

English 
Anthracite.  . 

2.4 

4.6 

8365 

8324  )  8  26 
8327  J  *62b 

-39 

O.SOOg.  Tart,  acid  + 
1.000  g.  Persulphate 

Belgium 
Braisette.  .  . 

2.4 

10.7 

7409 

7378  )  7QO, 
7409  }  7394 

-15 

O.SOOg.  Tartaric  acid 

Saar  coal  .... 

4.9 

11.7 

6594 

6634 

+  40 

0.500  g.  Tartaric  acid 

Cardiff  coal.  . 

2.2 

7.2 

7872 

7936 

+  64 

0.500  g.  Tartaric  acid 

Saar  coal.  .  .  . 

3.5 

8.4 

7146 

7161  )  ?184 
7207  \  7" 

+  38 

0.500  g.  Tartaric  acid 

Lignite 
Briquette.  .  . 

15.17 

5037 

5084  )  5Q76 
5068  (  5076 

+  39 

No    addition    but 
1.000  g.  of  coal  first 
dried  then  burned 

COMBUSTION  HEAT  AND  ITS  DETERMINATION        105 

Test-boilers  used  for  determining  the  thermal  value  of  fuels  on 
a  large  scale  differ  from  ordinary  boilers ;  the  heat-losses  in  com- 
mon boilers  are  not  sufficiently  uniform.  Therefore  an  especially 
constructed  calorimeter-boiler  has  to  be  used  (see  Muspratt). 

It  should  be  kept  in  mind  in  all  determinations  of  heating 
values  that  these  values  vary  with  the  pressure  and  the  tem- 
perature at  which  the  combustion  takes  place.  This  is  of 
importance,  as  we  can  hereby  calculate  the  thermal  efficiency  of 
a  fuel  under  different  conditions,  and  in  commercial  work,  where 
combustion  takes  place  at  constant  pressure,  the  figures  obtained 
in  the  bomb  (constant  volume)  have  to  be  corrected.  These 
variations  of  the  combustion  heat  are  based  on  the  well-known 
energy  principle :  the  sum  of  the  energy-quantities  accumulated 
in  the  interior  of  a  system,  when  the  latter  changes  from  one 
state  to  another,  is  exclusively  dependent  on  the  initial  and 
final  state  and  independent  of  the  intermediate  state.  In  the 
special  case  where  the  initial  and  the  final  state  are  alike  (cir- 
cular process),  this  sum  is  equal  to  naught. 

In  the  following  consideration  the  heat  generated  by  the 
system  and  delivered  outside  and  also  the  increase  of  volume  of 
the  system  is  taken  as  positive. 

Relations  between  combustion  heat  at  constant  volume  and  at 
constant  pressure.  The  combustion  heat  at  constant  pressure  is 
greater  than  at  constant  volume.  If  combustion  takes  place  at 
0°  C.  the  difference  of  the  two  combustion-heats  is,  in  cal.,  0.54 
times  the  contraction  of  molecular-volume  which  takes  place  in 
the  combustion. 

If  we  burn  a  gas-mixture  at  constant  pressure  we  obtain  a 
heat  quantity  Q.  At  first  the  volume  of  the  gas  is  increased  by 
the  heat,  then  it  decreases,  while  cooling  off  to  the  starting  tem- 
perature, to  a  volume  which  is  smaller  than  the  initial  volume. 
The  difference  of  volumes  corresponds  to  the  contraction  effected 
by  decrease  of  the  number  of  molecules  present  during  com- 
bustion. 

.If  we  allow  the  combustion  to  take  place  in  a  cylinder  (closed 
at  one  end,  and  fitted  with  an  air-tight  piston  which  can  move 
up  and  down  without  friction) ,  we  can  lift  this  piston  after  com- 
bustion and  when  the  gases  have  cooled  down  to  the  initial 
temperature,  so  that  the  products  of  combustion  occupy  the 
'  original  volume.  The  work  expended  thereby  is  APV. 


106  HEAT   ENERGY   AND  FUELS 

If,  however,  the  combustion  takes  place  at  constant  volume, 
the  heat  quantity  q  is  generated.  According  to  the  above 
explanations  we  have 

q  =  Q  -  APV, 

or  since 


we  have 

=  0-  — 

q  ==         428  ' 

If  the  system  contains  n  mols  we  have  according  to  Boyle-Gay- 
Lussac's  law, 

PV 


If  we  substitute  for 
T  =  273, 

P0  =  10,333  kg.  per  sq.  m., 
F0  =  0.02242  cu.  m., 
we  have 


1033  X  0.02242  X  273 

=  Q  —  n  - 
273  X  428 

=  Q  -  n  0.5411  cal. 

We  can  obtain  the  same  value  much  easier  by  considering  that 
we  have  for  1  mol  of  the  gases 

M  (cp  -  cv)  =  1.982  cal. 

and  that  the  gas-equation  referred  to  absolute  temperature  rests 
on  the  supposition  that  the  gas  laws  are  correct  down  to  absolute 
zero  and  that  the  gases  at  this  temperature  occupy  no  volume. 
We  have 

q  =  Q-  APV 
=  Q-M(cp-cv)T 
1.982  X  273 

1000 
=  Q  -  0.5411  cal.  per  mol. 


COMBUSTION  HEAT  AND  ITS  DETERMINATION         107 


This  equation  enables  us  to  transform  combustion  heats  obtained 
(in  the  bomb)  with  constant  volume  into  combustion,  heat  of 
constant  pressure.  Per  mol.  of  the  substance  burned  we  have : 


TABLE  XXXVI. 


Reaction. 

Combustion  Heat 

Contrac- 

at Constant 

tion 

in  Mols 

Volume. 

Pressure. 

H2  +  0  =  H20.. 
CO  +  O  -  CO2 

1.5 
0  5 

68.2 
67  9 

69.0 
68  2 

\  (H2  +  CO)  +  O 
CH2  +  2O2  =  CO2 

=  \  (H20  +  C02)  
+  2H2O  

1 
2 

68.0 
212.4 

68.5 
213.5 

*  (2C2H2  +  502)  = 

2CO2  +  H2O  

1.5 

314.9 

315.7 

All  these  calculations  refer  to  the  case  where  water  is  formed 
in  the  combustion  (upper  heat  value).  For  getting  the  lower 
heat  value  the  latent  heat  of  evaporation  of  water  (10.8  cal.  per 
mol)  has  to  be  deducted. 

It  follows  also  from  equation  pv  =  RT  that  wherever  1  mol 
of  a  gas  at  any  pressure,  p,  is  generated  or  disappears,  the 
external  work  pv  =  RT  =  1.982  T  cal.  will  be  consumed  or 
generated.  For  the  average  air-temperature  of  18°  C.  this 
quantity  of  work  therefore  is  1.982  (273  +  18)  =  582  cal.  In 
cases  where,  as  in  the  bomb,  the  gases  are  actually  generated  or 
disappear,  this  phenomenon  is  taken  into  account  by  the  com- 
bustion heat,  which  is  measured  directly.  This,  howrever,  is  not 
the  case  in  Parr's  calorimeter,  since  here  no  gaseous  oxygen  is 
originally  present  and  since  the  products  of  combustion  formed 
disappear  again.  The  determination  of  carbon  is  here  not 
affected,  the  formation  of  C02  taking  place  without  change  of 
volume.  It  is  different  with  hydrogen,  since  a  contraction 
takes  place  during  its  combustion,  but  not  in  Parr's  calorimeter. 
Therefore  this  calorimeter  does  not  give  the  combustion  heat 
at  constant  volume,  but  at  constant  pressure,  which  accounts  for 
the  fact  that  the  results  found  with  Parr's  calorimeter  are  higher 
than  the  results  found  with  the  bomb. 

The  following  law  can  be  derived  directly  from  the  energy 
principle  above  mentioned : 

The  heat  generated  in  a  direct  reaction  is  the  sum  of  all 
heat  quantities  that  are  generated,  provided  that  from  a  given 


108  HEAT  ENERGY  AND  FUELS 

initial  state  the  final  state  is  reached  by  various  consecutive 
reactions. 

This  law  can  be  used  for  calculating  reaction  heats  that  cannot 
be  measured  directly,  for  instance,  the  heat  of  formation  of 
carbon-monoxide : 

C  +  02  =  C02  generated q   =  94.3  cal. 

C  +  0    =  CO  generated ql  =  x      cal. 

CO  +  0    =  C02  generated. . . q2  =  68.2  cal. 

We  have  according  to  our  law, 

q  =  q,  +  qr 
Therefore 

1  =  94.3  -  68.2  =  26.1  cal. 

By  this  method  the  heat  of  formation  of  all  organic  compounds 
is  calculated  by  deducting  from  their  combustion-heats  the  heat 
of  the  elementary  components,  for  instance : 

C  +  H4  +  2  02  =  C02  +  2  H20g  =  94.3  +  2  X  69.0  =  232.3  cal. 
C  +  H4  =  CH4  q,  =x  cal. 

CH4  +  2  02        =  C02  +  2  H20g2  =  213.5  cal. 

1  =  232.3 2-  213.5  =  18.8  cal. 

Vice  versa  we  can  calculate  from  the  heats  of  formation  of 
organic  compounds  (which  are  found  in  the  thermo-chemical 
tables)  their  heats  of  combustion,  for  instance : 

C2(Diamond)  +  H2  =  C2H4  q  =  -  58.1  cal. 

2  C2  +  2  02  =  2  C02  qi=+ 188.6  cal.] 

H2  +  0  =  H20  (liquid)  &=  +  69.0  cal.j 

C2H2  +  5  O  =  2  C02  +  H20  (liquid)  q3  =         x 

3  =  188.6  +  69.0  -  (-  53.1)  =  315.7  cal. 

Relations  between  combustion  heat  and  combustion  tem- 
perature. The  combustion  heat  changes  with  the  temperature. 
The  change  depends  on  the  fact  whether  the  difference  of  specific 
heats  of  the  system  before  and  after  combustion  is  positive  or 
negative.  We  will  show  this  by  an  example : 


COMBUSTION  HEAT  AND  ITS  DETERMINATION         109 

We  will  calculate  the  combustion  heat  of  hydrogen  at  1000°  C., 
supposing  that  the  water  formed  remains  in  form  of  steam.  We 
have  then  at  15°  C. : 

H2  +  0  =  H20  (steam)  .  .  .  ql5  =  +  69.0  -  10.8  =  +58.2  cal. 

If  we  burn  the  hydrogen  at  15°  C.  and  heat  the  steam  formed  to 

1000  degrees,  we  have : 

,,1000 
ql6  _  I  cdt  =  58.2  -  11.0 

«M5 

=  47.2  cal. 

If  we  heat  hydrogen  and  oxygen  to  1000  degrees  and  then  burn 
them  at  this  temperature,  we  have 

/i  oo 
(c,  +  c2)  dt  +  g1000  =  -  (7.5  +  3.7)  +  ql(m 
.5 

-  -  11.2  +  g1000 
and  from  this : 

/1000 
(c  -c,  -cjdt  =  58.4  cal. 
,5 

In  this  case  the  difference  is  small,  in  others  much  greater. 
We  have,  for  instance,  for  CO  +  0  =  C02, 

1000 

?dt=  68.2  -  12.4 


=  55.8  cal. 

,1000 

f  ca)  dt  +  ql(m  =  g1000  -  11.1 

15 

and  therefore 

qm  =  66.9  cal. 


7! 

Ju 


If  we  indicate  the  heat-capacities  of  the  system  in  the  initial 
and  final  state  by  cl  and  cu  we  can  express  this  (KirchhofFs) 
law  by  the  general  formula : 

&  =  ft  +  (ci  +  CH)  tfi  -  0- 


CHAPTER  V. 

INDIRECT  METHODS   FOR  DETERMINING  THE  COMBUS- 
TION HEAT. 

(a)  Calculation  of  the  thermal  value  from  the  elementary 
analysis.  The  fuels  used  in  the  industries  are  mixtures  of 
different,  not  entirely  known,  chemical  compounds.  As  these 
compounds  have  different  thermal  values  it  is  evident  that  the 
calculation  of  the  thermal  value  from  the  elementary  analysis 
does  not  yield  exact  results.  Furthermore  the  making  of  an 
elementary  analysis  is  more  complicated  and  more  tedious  than 
the  combustion  in  a  bomb,  the  difficulty  of  getting  a  good  average 
sample  being  the  same  in  both  cases. 

For  certain  fuels,  however,  by  using  the  proper  empirical 
formula  a  result  can  be  obtained  that  is  sufficiently  good  for 
many  practical  purposes. 

For  bituminous  coal  the  following  formula  is  used  (Dulong) : 

8080  C  +  34600  (H  -  J  0) 

q- 


while  for  lignite,  peat  and  wood,  the  formula 

=  8080  C  +  29633  Ht  -  637  (W  +  Wt) 

q  =  100 

is  used. 

In  these  equations 
C  is  the  per  cent  of  carbon; 
H,  the  per  cent  of  hydrogen ; 
0,  the  per  cent  of  oxygen,  and 

Ht,  the  per  cent  of  disposable  hydrogen  (H,  =  H  -  £  0). 
W  means  the  per  cent  of  chemically  combined  water  (W  =  |  0). 
Wj  means  the  per  cent  of  hygroscopic  water. 

NOTE.  — Every  coal  —  even  dry  coal  —  contains  carbon,  oxygen  and  nitro- 
gen. It  was  formerly  thought  that  the  O  with  a  part  of  H  was  present 
as  chemically  combined  water.  The  excess  of  H  was  called  "disposable 
hydrogen." 

110 


METHODS  FOR  DETERMINING  COMBUSTION  HEAT       111 

8080  means  the  combustion  heat  of  carbon  (Favre  and  Silber- 

mann). 

34,600  means  the  combustion  heat  of  hydrogen  to  water. 
29,633  means  the  combustion  heat  of  hydrogen  to  steam. 
637  means  the  heat  of  evaporation  of  water. 

If  a  coal  contains  combustible  sulphur,  i.e.  sulphur  in  other 
form  than  sulphate,  some  heat  in  the  combustion  is  also  generated 
by  the  sulphur,  which  is  taken  into  consideration  by  adding  to 
the  above  formula  the  product  of  the  percentage  sulphur  S  by 
W  cal. 

(b)  Berthier's  method  for  determining  the  thermal  value. 
Berthier's  method  is  based  on  the  determination  of  the  oxygen- 
quantity  required  for  the  complete  combustion  of  the  fuel  and 
on  Welter's  law,  the  incorrectness  of  which  was  proven  long  ago. 
This  method  however  is  still  in  use  on  account  of  its  extraordinary 
simplicity.  Welter  supposed  that,  by  burning  a  certain  and 
constant  quantity  of  oxygen  with  any  other  element,  always  the 
same  amount  of  heat  would  be  generated.  This  however  is  not 
the  case,  since  1  kg.  of  oxygen  in  combination  with  the  following 
substances  generates  the  following  amounts  of  heat : 

Carbon  to  carbon  dioxide 3030  cal. 

Hydrogen  to  water 4272  cal. 

Hydrogen  to  steam 4192  cal. 

As  Berthier's  calculation  is  based  on  the  quantity  of  heat 

corresponding  to  the  combustion  of  carbon  to  carbon  dioxide  by 
means  of  oxygen,  it  is  evident  that  the  results 
will  generally  be  too  low  and  the  lower  the 
more  disposable  hydrogen  is  contained  in  the 
fuel.  Berthier  proceeded  as  follows:  1  g.  (of 
graphite  0.5  g.)  of  the  finely  ground  fuel 
is  weighed  exactly  and  mixed  with  sifted 
litharge,  which  is  free  of  metallic  particles. 
The  mixture  is  put  into  a  test-cup  (Fig.  29), 
covered  with  from  20  to  25  g.  of  litharge,  care- 
fully put  into  a  red-hot  muffle-furnace,  covered 

FIG.  29! —  Berthier's  an<^  quickly  heated  to  red -glow;  in  from 
Coal  Tester.  three-fourths  to  one  hour  the  operation  is 

finished  and  the  litharge  according  to  the  fuel  quantity  reduced, 

by  oxidizing  the  fuel : 

2  PbO  +  C  =  2  Pb  +  CO,. 


112  HEAT  ENERGY  AND  FUELS 

From  the  weight  of  the  metallic  lead  obtained,  the  quantity  of 
oxygen  combined  with  the  fuel  can  be  calculated.  The  test-cup 
is  now  removed  from  the  muffle,  shaken  up  several  times  to 
combine  the  small  lead-particles,  that  may  be  distributed  through 
the  litharge,  with  the  main  lead  mass  and  allowed  to  cool.  The 
cup  is  now  broken,  the  piece  of  lead  brushed  clean,  and  the 
litharge  examined  for  particles  of  lead. 

In  calculating  the  thermal  value,  the  hydrogen  present  is 
not  taken  into  consideration,  i.e.  it  is  assumed  that  only  the 
oxygen  has  combined  with  carbon.  Since  1  kg.  carbon  re- 
duces about  34  kg.  of  lead  and  yields  by  combustion  8080 
cal.,  the  weight  of  the  lead  obtained  is  simply  divided  by 
34  multiplied  by  8080  for  getting  the  absolute  thermal 
value  of  the  fuel  in  question.  Sulphur  would  have  to  be 
determined  separately  and  taken  into  consideration  as  explained 
above. 

Various  modifications  of  Berthier's  test  were  recommended. 
Forchhammer  suggested  the  use  of  oxychloride  of  lead  in  place 
of  litharge.  Munroe  uses  instead  of  the  test-cup  a  gas-pipe 
provided  with  a  plug  at  one  end,  while  Strohmeyer  oxidizes  the 
fuel  by  means  of  cupric  oxide,  treating  the  residuum  with  hydro- 
chloric acid  and  ferric  chloride  and  determining  the  ferrous 
chloride  formed  by  titration. 

(c)  Other  empirical  methods  for  determining  the  fuel  value.  An 
important  advance  is  the  empirical  formula  of  Dr.  Otto  Gmelin, 
based  upon  a  few  simple  operations,  which  gives  very  much 
better  results  than  Berthier's  process. 

Gmelin  assumed  that  the  coals  are  mixtures  of  various  chem- 
ical compounds,  which  compounds  differ  from  each  other  not 
only  chemically,  but  also  physically.  He  selected  such  a  physical 
property,  the  ability  of  retaining  hygroscopic  water  and  based 
his  empirical  formula  upon  this  property: 

q  =  [100  -  (H20  +  "ash")]  80-  C  (6  HaO), 

in  which  equation  H20  means  the  hygroscopic  water,  "ash, "  the 
ash-content  of  the  fuel  in  per  cent  and  C  a  coefficient  which 
changes  with  the  moisture  of  the  coal  and  has  the  following 
values : 


METHODS  FOR  DETERMINING  COMBUSTION  HEAT     113 

Hygroscopic  water  below  3  per  cent C  =  -     4 

Hygroscopic  water  between  3  and  4.5  per  cent.  .  C  =  +    6 

Hygroscopic  water  between  4.5  and  8.0  per  cent  C  =  +  12 

Hygroscopic  water  between  8.5  and  12.0  per  cent  C  =  +  10 

Hygroscopic  water  between  12  and  20  per  cent .  C  =  +    8 

Hygroscopic  water  between  20  and  28  per  cent .  C  =  +    6 

Hygroscopic  water  over  28  per  cent C  =  +    4 

Seven  years  later  the  author  tried  to  utilize  more  simple 
properties  that  would  be  more  independent  of  accidental  circum- 
stances than  the  moisture,  and  also  be  related  to  the  chemical 
composition  and  therefore  to  the  combustion-heat  of  the  fuels. 
He  selected  the  behavior  of  fuels  in  dry  distillation  and  the 
determination  of  the  oxygen  required  for  complete  combustion. 
He  proceeds  as  follows: 

About  1  g.  of  the  finely  powdered  fuel  is  weighed  in  a  platinum- 
crucible  and  —  after  determining  the  moisture  W  by  drying 
at  100°  C.  —  is  heated  (observing  ordinary  precautions)  until 
combustible  gases  are  given  off.  The  loss  of  weight  in  per  cent 
represents  the  gas-yield  G.  The  residuum  P  per  cent  is  now 
completely  burned  in  the  open,  inclined  crucible  whereby  the 
ash  content  A  and  the  fixed  carbon  or  coke-carbon  K  is  found. 
The  latter  however  always  contains  negligible  quantities  of 
oxygen,  hydrogen  and  nitrogen. 

The  quantity  of  oxygen  required  S  is  most  conveniently 
determined  with  about  5  g.  of  fuel  by  Berthier's  method. 

The  quantity  of  oxygen  required  for  burning  the  fixed  carbon 
is  found  by  the  following  equation : 

o2  ^        o  _, 


The  oxygen  for  completely  burning  the  gaseous  products  of 
distillation  is  : 


The  combustion  heat  of  the  fixed  carbon  was  (as  average) 
empirically  determined  as  7630  cal.  per  1  kg.  of  carbon,  while 
the  combustion  heat  of  the  gaseous  products  of  distillation  varies 


114 


HEAT  ENERGY  AND  FUELS 


according  to  the  quality  of  coal  and  composition  of  the  gases  of 
distillation. 
The  nature  of  a  fuel  is  indicated  by  the  ratio  (weight)  of 

/C\ 
gaseous  products  of  distillation  and  fixed  carbon  f  —  J;  and  even 

more  so  by  the  ratio  of  the  oxygen  required  for  the  volatile 

/S  N 
matter  to  the  oxygen  required  for  the  fixed  carbon  (  — )  •    The 


latter  ratio  is  used  empirically  for  determining  the  thermal- 
value  of  a  fuel  by  means  of  the  equation  : 


wherein  C  is  a  coefficient,  the  value  of  which  depends  on  the 

o 

quality  of  the  fuel  (wood,  peat,  lignite,  coal)  and  the  ratio  -    . 


TABLE  XXXVII. 

RATIO  OF  Sg  TO  Sfc. 


Sg 

Values  of  C  for 

sk 

Wood  and 
Peat. 

Lignite. 

Bitum. 
Coal. 

0.25 

5500 

5600 

0.50 

4930 

4300 

3500 

1.00 

4830 

3420 

3250 

1.50 

4750 

3350 

3225 

2.00 

4660 

3350 

3210 

2.50 

4570 

3360 

3200 

3.00 

4470 

3370 

3180 

3.50 

4360 

3170 

4.00 

4255 

3500 

3150 

4.50 

4150 

3140 

5.00 

4045 

3700 

3130 

5.50 

3940 

3120 

6.00 

3830 

3950 

3100 

6.50 

3080 

7.00 

3070 

7.50 

3060 

8.00 

3050 

In  order  to  make  the  formula  independent  of  the  kind  of  fuel 
and  to  base  the  calculation  of  the  thermal  value  entirely  upon 
the  content  of  moisture,  ash,  gas,  fixed  carbon  and  oxygen 
required  for  combustion,  the  different  fuels  were  divided  into 


METHODS  FOR  DETERMINING  COMBUSTION  HEAT     115 


four  groups  according  to  their  ability  to  give  off  gas  when  dry 
and  free  of  ash  and  the  value  of  C  calculated  for  each  of  the 

S 

groups  according  to  the  different  values  of  -^  •    The  following 

&k 

table  —  by  means  of  which  the  thermal  value  can  be  determined 
without  any  knowledge  of  the  quality  of  the  fuel  —  is  easily 
understood. 

TABLE   XXXVIII. 

DATA  FOR  DETERMINING  THERMAL   VALUES. 


GROUP 

I 

II 

III 

IV 

Gas  given  off 
by  the  Fuel 
(dry  and 
free  of  ash). 

0  -  33% 

33-47.5% 

47.5-75% 

75-  100% 

gg 
8k 

Values  of  the  Coefficient  C. 

0.10 
0.15 
0.20 
0.25 
0.30 
0.35 
0.40 
0.45 
0.50 
0.54 
0.55 
0.60 
0.70 
1    0.80 
0.90 
1.00 
.     1.5 
2.0 
2.5 
3.0 
3.5 
4.0 
4.5 
5.0 
5.5 
6.0 

4900 
4550 
4230 
3960 
3730 
3540 
3380 
3250 
3150 
3086 
3070 
3000 
2900 
2850 
2850 
2850 

5100 
4800 
4500 
4220 
4010 
3850 
3710 
3600 
3512 
3490 
3400 
3280 
3210 
3166 
3130 
2955 

5250 
4900 
4600 
4350 
4170 
4020 
3932 
3910 
3820 
3690 
3600 
3558 
3550 
3550 
3550 

5050 
4815 
4619 
4480 
4230 
4170 
4120 
4070 
4020 
3970 
3920 
3870 
3820 
3770 

The  following  empirical  formulas  have  since  been  proposed 
By  G.  Arth: 

=  34,500  (H  -  I  0)  +  8080  C  +  2162  S 

q~  100 


116  HEAT   ENERGY  AND   FUELS 

By  E.  Goutal  (a  modification  of  Jiiptner's  formula)  : 
q  =  8150  C  +  AM. 

M  is  the  quantity  of  volatile  matter,  A  a  coefficient  the  value 
of  which  is  : 

Volatile  substances  =    2  to  15  per  cent.  .  .  .  A  =  13,000 

Volatile  substances  =  15  to  30  per  cent.  .  .  .  A  =  10,000 

Volatile  substances  =  30  to  35  per  cent.  .  .  .  A  =     9500 

Volatile  substances  =  35  to  40  per  cent.  .  .  .  A  =     9000 

The  international  union  of  the  steam-boiler-inspection  societies 
has  adopted  the  following  formula  : 


=  [SOOO  C  +  2900  (  H  -  -  } 
L  \  8  / 


2500  S  -  600  lp* 

100 


in  which  W  means  the  quantity  of  hygroscopic  water.  The 
differences  against  direct  calorimetric  determinations  are  (L.  C. 
Wolff)  : 

For  bituminous  coal  .................  ±     2  per  cent 

For  lignite  .........................  ±     5  per  cent 

For  peat  ...........................  ±     8  per  cent 

For  cellulose  .......................  -  7.9  per  cent 

For  wood  ........  .  ..................  ±   12  per  cent 

By  D.  Mendeleeff  :  q  =  81  C  +  300  H  -  26  (0  -  S). 

D.  de  Paepe  has  substituted  for  the  value  M  in  Goutal  's 

f  .        100  M 

formula  the  expression  —  -  -  - 

SUGGESTIONS  FOR  LESSONS. 

Practice  in  handling  various  combustion-calorimeters;  deter- 
mination of  water-value  and  error-limit. 

Comparative  determination  of  the  combustion  heat  by  different 
methods. 

Calculation  of  combustion  heat  at  constant  pressure  from  the 
combustion  heat  at  constant  volume  and  vice  versa. 

Calculation  of  combustion  heats  for  given  combustion  tem- 
peratures. 


CHAPTER  VI. 


INCOMPLETE   COMBUSTION. 

THE  complete  combustion  of  the  fuels  used  in  the  industries 
yields  carbon  dioxide  and  water.  The  chemical  composition  of 
the  fuel  being  known,  the  quantity  of  oxygen  theoretically 
required  for  complete  combustion  is  easily  calculated.  This 
quantity  is  called  the  theoretical  quantity  of  oxygen  necessary  for 
complete  combustion.  The  average  composition  of  dry  air,  free 
of  carbon  dioxide,  being 


Oxygen. . 
Nitrogen. 


21  per  cent  vol.         23  per  cent  weight 
79  per  cent  vol.         77  per  cent  weight 


it  is  a  simple  matter  to  calculate  the  theoretical  quantity  of  air 
required  for  complete  combustion. 

(In  many  cases  it  is  sufficient  to  calculate  approximately  and  to  assume 
the  composition  of  air:  20  per  cent  vol.  O  and  80  per  cent  vol.  N.)  The 
CO2  content  of  the  air  varies  from  0.04  to  0.06  per  cent.  In  densely  inhab- 
ited buildings  it  can  go  as  high  as  0.5  and  even  0.9  per  cent  vol.  The 
quantity  of  moisture  in  the. air  varies  considerably.  Air  saturated  with 
moisture  contains  per  1  cu.m. 


Degrees  C 

g.  H20. 

Degrees  C. 

g.  H20. 

-10 
0 

+   5 
+  10 
+  15 
+  20 

2.284 
4.871 
6.795 
9.36-2 
12.746 
17  157 

+  25 
+  30 
+  35 
+  40 
+  100 

22.848 
30.095 
39.252 
50.700 
588.730 

The  moisture  of  the  air  is  generally  below  saturation  and  above  ^  the 
quantity  required  for  saturation. 

In  heating  tests  the  moisture  of  the  air  has  to  be  determined  by  means 
of  a  hygrometer  or  psychrometer. 

In  practice,  however,  this  theoretical  quantity  of  air  is  not 
sufficient  for  complete  combustion  and  therefore  an  excess  of  air 
has  to  be  used. 

117 


118  HEAT  ENERGY  AND  FUELS 

The  reason  for  this  is  the  difficult  and  incomplete  mixture  of 
the  gases  to  be  burned  with  the  combustion  air  and  the  occurrence 
of  incomplete  reactions. 

The  incomplete  combustion  can  therefore  furnish  various 
products,  as  follows: 

CO,  or 


C  +  0 


C2H4  +  0 


}  C02  +  J  C 

•>  (~^(~\       I     o  TT      /-vi» 

1  v^v/9  ~T~  ^  -*"i-9}  or 

2  CO  +  2  H20 
CO  +  CH4,  or 

CO  +  C  +  2  H2,  or 
C2H2  +  H20,  etc. 


The  number  of  different  reactions  that  can  take  place  simul- 
taneously and  in  parallel  is  frequently  very  great.  The  number 
of  reactions  and  the  quantity  of  products  depend  on  the  pre- 
vailing conditions. 

In  all  these  cases  we  speak  of  a  chemical  equilibrium  which 
depends  on  the  so-called  equilibrium-conditions.  Such  condi- 
tions are:  Temperature,  pressure,  electric  state  and  the  mutual 
relation  of  the  elementary  components  present,  i.e.  the  concen- 
tration. By  a  change  of  the  conditions,  the  state  of  equilibrium 
is  changed  as  follows  (Henry  Le  Chatelier) : 

Any  change  in  an  equilibrium  factor  causes  a  change  in  the 
system  which  is  directly  opposite  to  the  change  in  the  factor. 

This  law  is  best  explained  by  an  example : 

1.  Any  increase  of  temperature  causes  a  change,  which  tends 
to  decrease  the  temperature  of  the  system  and  vice  versa. 
Example : 

(a)  Dissociation: 

C02  -»  CO  +  0  -  68.2  cal. 
H20  ->  H2  +  O  -  58.2  cal. 

In  both  reactions  heat  is  absorbed  and  therefore  both  are 
caused  or  facilitated  by  increase  of  temperature. 
The  reaction 

2  CO  -» C  +  C02  +  42.0  cal. 

in  which  heat  is  liberated,  is  facilitated  by  decrease  of  tem- 
perature.    Carbon  monoxide  is  therefore  more  stable  at  high 


INCOMPLETE  COMBUSTION  119 

than  at  low  temperatures.     In  the  presence  of  platinum,  iron  or 
especially  nickel  in  fine,  spongy  form  this  reaction  takes  place 
completely  at  about  300°  C. 
(6)  Incomplete  reactions : 

C02  +  H2  -» CO     +  H2O  -  10  cal. 
CH4  +  CO  ->  C2H2  +  H20  -  39  cal. 

In  both  reactions  absorption  of  heat  takes  place;  they  are 
therefore  caused  and  facilitated  by  increase  of  temperature. 
At  low  temperature  more  C02  +  H2,  or  CH4  +  CO;  at  high 
temperature  more  CO  +  H20  or  C2H2  +  H20,  will  be  present. 

The  reaction 

CO  +  H20  -»  C02  +  H20  +  10  cal. 

will  naturally  be  facilitated  by  lowering  the  temperature. 

2.  Any  increase  of  outside  pressure  causes  a  change  of  equi- 
librium, by  which  the  pressure  is  decreased  and  vice  versa. 
Examples : 

(a)  Dissociation: 

2  C02  -*  2  CO  +  02 
2  H20  ->  2  H2  +  02. 

By  the  dissociation  of  C02  or  H20  the  volume,  or  (at  constant 
volume)  the  pressure  is  increased  50  per  cent.  The  dissociation 
will  therefore  increase  with  decreasing  pressure  and  decrease 
with  increasing  pressure. 

(6)  Incomplete  reactions : 

C2H2  +  H2-»CH4  +  C. 

The  volume  of  solid  carbon,  which  is  exceedingly  small,  need 
not  be  considered.  The  volume,  however  (or  at  constant 
volume  the  pressure),  of  the  CH4  formed  is  only  half  of  the  volume 
of  the  original  mixture  of  C2H2  and  H2.  The  reaction  is  there- 
fore facilitated  by  increasing  the  pressure.  This  is  proven  by 
explosion  in  closed  vessels,  whereby  the  quantity  of  CH4  and  C 
increases  with  the  pressure. 

The  equilibrium 

CO  +  H20  +±  C02  +  H2 

is  (if  the  water  is  in  form  of  steam)  independent  of  the  pressure, 
as  we  have  on  both  sides  the  same  volume  and  therefore  also  the 
same  pressure. 


120  HEAT  ENERGY  AND  FUELS 

The  reaction 

2  CO  =  C  +  C02 

is  decreased  by  decreasing  the  pressure  because  the  volume  and 
therefore  also  the  pressure  of  C02  is  only  half  that  of  2  CO. 

3.  Any  increase  in  concentration  of  a  substance  in  a  system 
causes  a  change  in  the  state  of  equilibrium,  in  which  a  certain 
quantity  of  this  substance  is  removed  and  vice  versa  (mass- 
action).  The  quantitative  expression  for  the  relations  between 
chemical  equilibrium  and  equilibrium-conditions  is  different  if 
the  equilibrium  at  a  certain  temperature  or  the  equilibrium  at 
any  temperature  is  considered.  In  the  first  case,  i.e.  for  the 
isothermic  equilibrium,  the  law  of  mass-action;  in  the  second, 
general  case,  van't  Hoff's  or  Le  Chatelier's  equation  has  to  be 
applied. 

For  gas-mixtures  the  latter  equation  is  preferable  as  the 
numerical  concentration  results  directly  from  the  volumetric 
composition  of  the  gases. 

We  want  to  consider  now  an  example  of  great  importance  in 
the  industries. 

DISSOCIATION  OF  CARBON  DIOXIDE. 

•  At  high  temperature  carbon  dioxide  is  decomposed  according 
to  the  equation : 


If 

RJ 


Le  Chatelier's  equation  in  general  form  is : 
QTdT 


+  (N"-N')  IP  +       n2l  C2-  ^X/ C,  =  constant. 


In  this  equation  QT  stands  for  the  total  heat  of  reaction  (sum 
of  heat  generated  and  external  work  performed  by  the  reaction, 
both  expressed  in  cal.)  at  the  temperature  T,  P  is  the  pressure 
of  the  system,  N"  and  N'  the  number  of  molecules  on  the  right 
and  left  side  of  the  equation,  nl  anU  n2  the  number  of  molecules, 
C1  and  C2  the  concentrations  of  the  different  substances  taking 
part  in  the  reaction,  index  1  meaning  the  initial  system,  and  2  the 
final  system. 


INCOMPLETE  COMBUSTION  l2l 

If  we  use  the  common  instead  of  the  natural  logarithms  and 

if  we  make  —  =  500,  we  can  write  our  equation  : 
H 


500  +  2.3026  (N"~  N')  log  P  +  2.3026          2  log  C2 

-5^  log  Cj  =  constant. 


N"  -  N'  =  1.5  -  1  =O.5, 
therefore 

L  log  Cj  =  log  /£  =  log 


If  we  make  the  total  concentration  of  the  system  after  the 
establishment  of  equilibrium  =  1,  we  have 


Assuming  that  no  surplus-oxygen  is  present,  we  conclude 
from  the  reaction  equation  : 

C,,  =  JCM.  (2) 

We  call  x  the  ratio  between  the  dissociated  carbon  dioxide, 
(i.e.  the  carbon  monoxide  formed)  and  the  quantity  of  C02 
that  would  be  present  if  no  dissociation  had  taken  place,  i.e. 
Cco  +  CC02,  the  coefficient  of  dissociation,  and  we  have 

x  =  _    Cco-      •  (3) 


There  can  be  deduced  from  (1)  and  (2)  the  following  equations 

+  f  <?co 

=   -"•          2 


CC02  +  f  <?co  =  1 


and  therefore 


_ 


122  HEAT   ENERGY   AND  FUELS 

from  this 


or 

r  x         2x  c  x 

0  x      2  +  x^  2        2  -f  x 

1+2 
and 

9  T  9  C\    —   r"i 

Z  X  Z  11          X) 


°°*  (2  +  x)         (2  +  x) 

By  substituting  these  three  values,  we  have 
(CJ  (CJ* 


For  finding  the  constant  the  following  observations  of  Henry 
Sainte-Claire-Deville  are  used  : 

P  =  1  at. 

T  =  3000  +  273  =  3273. 

x  =  0.40. 

If  we  assume  (in  accordance  with  Le  Chatelier)  the  total  heat 
of  reaction  of  the  reaction  CO  +  0  —  >  C02  to  be  independent  of 
temperature,  and  taking  Q  =  68.2  cal.,  we  have 

fiT  x^ 

+  1.1513  log  P  +  2.3026  log   (1  _  x)  (2  +  ^ 
=  Constant; 
or  as  for        P  =  1  at.,  log  P  =  0. 


therefore 
-  34100 


Constant=  -     ^rp    t  2.3026  log  Q  ^      =  -  11.7192; 
+  1.1513  log  P  +  2.3026  log  K  =  -  11.7194, 


T 

or 

14809 


logK  -  (^°  _  1L7i92  -  1.1513  log  P)  ^ 


.3026 
-  5.0895  -  0.5  log  P. 


INCOMPLETE  COMBUSTION 


123 


From  this  Le  Chatelier  has  calculated  the  values  of  x  given  in 
Table  XXXIX. 

TABLE   XXXIX. 

COEFFICIENTS  OF  DISSOCIATION. 

(Le  Chatelier). 


Temperature 
Degrees  C. 

Pressure  in  Atmospheres. 

0.001 

0.01 

0.  1 

1 

10 

100 

1000 
1500 
2000 
2500 
3000 
3500 
4000 

0.007 
0.07 
0.40 
0.81 
0.94 
0.96 
0.97 

0.003 
0.035 
0.125 
0.60 
0.80 
0.85 
0.90 

0.0013 
0.017 
0.08 
0.40 
0.60 
0.70 
0.80 

0.0006 
0.008 
0.04 
0.19 
0.40 
0.53 
0.63 

0.0003 
0.004 
0.03 
0.09 
0.21 
0.32 
0.45 

0.00015 
0.002 
0.025 
0.04 
0.10 
0.15 
0.25 

The  results  of  these  calculations  agree  with  the  observations 
made  at  1500°  C.  on  the  density  of  carbon  dioxide. 

If  we  keep  in  mind  that  it  is  the  partial  pressure  of  carbon 
dioxide  that  is  dealt  with  here,  we  can  make  from  the  above 
table  the  following  conclusions,  which  are  of  importance  in 
practice : 

1.  Smelting  furnaces.     In  smelting  furnaces  the  maximum 
temperature  reached  is  2000°  C.,   and  the  maximum  partial 
pressure  of  carbon  dioxide  is  about  0.2  at.    There  is  therefore 
about  5  per  cent  of  the  latter  dissociated,  which  decreases  the 
capacity  of  the  furnace  to  a  small  extent  (maximum  ^V,  but 
generally  much  less  on  account  of  the  excess  of  air  used,  which 
diminishes  the  dissociation  of  carbon  dioxide). 

2.  Illuminating  flames.    The  luminous  flame-zone,  in  which 
the  separated  carbon  is  burned,  seems  to  have  in  ordinary 
flames  a  temperature  of  about  2000°  C. ;  in  regenerative-burners 
the  temperature  is  higher.     On  account  of  the  high  percentage 
of  hydrogen  in  illuminants,  the  C02  —  partial  —  pressure  falls 
below  0.1  at.    Therefore  the  dissociation  can  go  above  10  per 
cent,  the  flame-temperature  decreasing  accordingly.     The  illu- 
minating power,  which  increases  much  faster  than  the  temper- 
ature, decreases  to  a  much  larger  extent,  which  shows  that  the 
dissociation  is  an  important  factor  in  illuminating  flames. 


124  HEAT  ENERGY  AND  FUELS 

3.  Explosives.  Their  combustion- temperature  is  in  most 
cases  below  2500°  C.  and  always  below  3000°  C.  As  the  pressure 
of  carbon  dioxide  herein  goes  into  thousands  of  atmospheres, 
the  dissociation  does  not  have  to  be  considered. 

On  account  of  the  very  high  pressures,  in  using  the  equili- 
brium equations  for  explosives,  the  law  of  Boyle-Gay-Lussac 
(PV  =  nRT)  must  not  be  used ;  it  is  necessary  to  introduce  into 
the  equation  a  constant  b : 

P(V  -b)  =  nRT. 

Similar  conditions  prevail  in  the  dissociation  of  water.  As 
we  have  seen  above,  we  have  (if  no  excess  of  oxygen  is  present) : 

2x  x 

C co  =;;-—->  quantity  of  oxygen  =  — - - 


x 


2  +  x  2  +  x 

and 

-         2  (1  -  x)  =  2  (1  -  x) 

2 + x  2+x 


Sum  =   _ — 


If  we  have  (n  +  1)  times  the  quantity  of  oxygen,  the  equation 
for  the  reaction  reads  as  follows : 

CO,  +  (n)  02  =  CO  +  (n  +  J)  02 

and  we  have,  after  the  equilibrium  has  been  established, 
x*  mols  CO 
(1  -  x9)  mols  C02 

-  +  n  }  mols  02 


INCOMPLETE  COMBUSTION  125 

and  therefore 

-  x'  2* 


Therefore 


»2 

cm  =- 

2- 

^  +  2n 

**& 
1  -  x7 

2  +  a/  +  2n 
n 

2  (1  -  z') 

^ 

h  2" 

/ 

2  +  ^  +  271 
2  xf          /     x'  +  2  n     Y 

(CJ  (Cg» 

2  +  '. 

c'  +  2  n  \2  +  x'  +  2  n  / 

x'   (     ^ 

+  2n 

2  (1  -  z') 

2  +  a/  +  2  n 
/                  ^  +  a/(2n)» 

V2  + 

xf  +  2ri 

1  -  xf  (I  -  xf)  (2  +  ^  +  2  n)* 

As  K  necessarily  has  the  same  value  as  in  the  former  case, 
we  can  say : 

x*  x'*  +  x'  (2  n)*          u 

(1  -  x)  (2  +  x)*  ~  (1  -  z')  (2  +  xf  +  2  n)*  ' 

If  we  had  used  twice  the  theoretical  amount  of  oxygen,  n 
would  have  been  equal  to  one  (n  =  1)  and  we  would  have 

x*  xf*  +  x'V2  <  x'*  +  x'  \/2 


(1  -  x)  (2  +  «)*         (1  -  xf)  (2  +  x'  +  2)*      (1  -  a/)  (4  + 

a/*  +  1.4142  £' 

=  (1  -  xf)  (4  + 


126  HEAT   ENERGY  AND  FUELS 

We  found  (see  above)  i  =  0.05  for  C02  at  2000°  C.  and  0.2  at 
partial  pressure.     Substituting  this  value,  we  get  : 

0.05*  xf*  +  1  4142  x' 


an  equation  from  which  x'  can  easily  be  calculated.     We  see  at 
a  glance  that  x'  is  smaller  than  x. 


CHAPTER  VII. 
COMBUSTION-TEMPERATURE. 

THE  maximum  temperature  that  a  fuel  could  produce  if 
burned  completely,  without  any  loss  of  heat,  with  the  theoretical 
quantity  of  air,  we  call  pyrometric  heating-effect.  It  is  gener- 
ally calculated  from  the  equation  : 


wherein  q  stands  for  the  quantity  of  heat  generated  by  com- 
bustion, and  c  and  p  for  the  specific  heat  and  the  quantity  of 
components  contained  in  the  products  of  combustion  respec- 
tively. This  temperature  however  can  never  be  attained  in 
practice. 
The  temperatures  of  industrial  fires  and  fire-places  depend  on  : 

1.  The  quantity  of  heat  furnished  by  the  fuel,  which  consists  of 

.     (a)  The  heat  of  combustion  proper  and 

(6)  The  heat  previously  stored,  i.e.  the  heat-content  of 
the  substances  used. 

2.  The  heat  carried  away   by  the  products  of  -combustion 
which  may  be  latent  (for  instance,  CO  leaving  a  blast-furnace). 

3.  The  heat  lost  by  radiation. 

4.  The  heat  generated  or  absorbed  by  the  substances  to  be 
treated. 

5.  The  quantity  of  heat  used  for  forming  and  expanding  the 
gases  generated  in  the  fire. 

There  is  a  relation  between  all  these  quantities,  which  can  be 
deduced  from  the  principle  of  conservation  of  energy. 

Proceeding  from  the  fuel,  air  and  substances  to  be  worked,  in 
the  first  stage,  the  sum  of  all  heat-quantities  introduced  into  or 
generated  in  the  fire,  is  independent  of  the  order  in  which  the 
transformations  take  place,  depending  only  on  the  first  and  last 
stage. 

127 


128  HEAT  ENERGY  AND  FUELS 

We  therefore  can  say  that  the  quantity  of  heat  introduced 
into  the  furnace  is  equal  to  the  quantity  taken  out  of  the  furnace. 

The  heat  introduced  into  or  generated  in  the  furnace  equals 
the  heat  taken  from  the  furnace. 

These  quantities  of  heat  consist  of : 

1.  Heat  introduced  into  the  furnace  by  fuel,  air  and  sub- 
stances to  be  worked  (by  their  own  temperature). 

2.  Heat  of  combustion. 

3.  Heat  of  reaction  of  the  substances  to  be  worked. 

4.  Heat  content  of  the  combustion  gases. 

5.  Heat  content  of  the  finished  products. 

6.  Loss  of  heat  by  radiation. 

Since  the  absolute  heat-content  of  the  substances  as  they 
enter  or  as  they  leave  the  furnace  cannot  be  determined,  we  have 
to  be  satisfied  with  a  relative  determination  generally  referred 
to  a  certain  normal  condition,  which  serves  as  a  base  for  the  cal- 
culations. As  such  the  temperature  of  melting  ice  is  generally 
used. 

Let  us  imagine  an  ideal  furnace  which  perfectly  insulates  the 
heat  and  in  which  no  working  products  are  present.  If  we 
introduce  into  this  furnace  fuel  and  air  of  a  certain  temperature 
(say  0°C.),  allow  combustion  of  same  and  then  cool  the  com- 
bustion gases  to  the  initial  temperature  (0°  C.),  we  have  the 
equation : 

Heat  of  combustion  =  Heat  of  cooling. 

A.  The  heat  of  comb.ustion  is  a  known  quantity.  The  heat 
of  cooling  is  the  difference  of  the  heat-content  of  the  combustion 
products  at  the  temperature  at  which  they  leave  the  furnace 
and  at  the  starting  temperature  (here  0°  C.),  to  which  we  imagine 
them  cooled  again  in  the  end.  In  our  ideal  furnace,  the  heats 
of  combustion  and  of  cooling  are  equal.  The  products  of  com- 
bustion leave  the  furnace  at  the  combustion  temperature,  which, 
as  we  will  see,  is  easily  calculated. 

The  heat  content  is  equal  to  the  weight  of  the  combustion  prod- 
ucts multiplied  by  their  specific  heat  and  their  temperature.  If 
we  use  the  absolute  temperature,  we  obtain  the  total  heat  con- 
tent; if  we  use  the  temperature  in  centigrade  we  obtain  the  heat- 
quantity,  by  which  the  substance  in  question  is  richer  than  at 
0°C. 


COMBUSTION -TEMP  ERA  TURE 


129 


In  calculating  the  pyrometric  heating  ,  effect,  formerly  the 
specific  heat  was  taken  as  constant,  i.e.  independent  of-  tem- 
perature. The  following  are  the  figures  used : 

TABLE   XL. 

SPECIFIC    HEAT    OF    GASES   AND    VAPORS    AT    CONSTANT    PRESSURE 
(Referred  to  Unit  Weight.) 


Name. 

Interval 
of  Tem- 
perature. 
Degrees. 

Specific 
Heat. 

Observer. 

Air  
Air  

0—100 
0  —  200 

0.23'741 
0  23751 

Regnault 

Oxygen  
Nitrogen  
Hydrogen  .  . 

13—207 
0—200 
12  198 

0.21751 
0.2438 
3  4090 

a 

Carbon  monoxide  
Carbon  monoxide 

23—  99 
26  198 

0.2425 
0  2426 

Wiedemann 

u 

Carbon  dioxide  
Carbon  dioxide  
Water  Vapor  
Methane  
Ethylene  

15—100 
11—214 
128—217 
18—208 
24—100 

0.20246 
0.21692 
0.48051 
0.59295 
0.3880 

Regnault 

H 

(i 
it 

Wiedemann 

By  means  of  these  figures  the  temperature  of  combustion  of 
carbon  in  pure  oxygen  is  calculated  as  follows: 


t  = 


8080 


=  10201°  C.* 


3.667  X  0.217 

The  combustion  of  coal  in  the  theoretical  amount  of  air  should 
give: 


t  = 


8080 


=  2719°  C.f 


3.667  X  0.217  +  8.929  X  0.244 

while  the  combustion  of  carbon  with  double  the  volume  of  air 

would  yield  J 

8080 

3.667  X  0.217  +  8.929  X  0.244  +  11.596  X  0.238 
8080 


0.792  +  2.179  +  2.760 


1410°  C. 


*  By  the  combustion  of  1  kg.  carbon  to  CO2  8080  cal.  are  generated; 
3.667  kg.  CO2  are  thereby  formed,  having  a  specific  heat  of  0.217. 

t  8.929  kg.  nitrogen  are  present  in  the  air  of  combustion  besides  2.667  kg. 
oxygen. 

|  11.596  kg.  is  the  weight  of  the  surplus  air. 


130 


HEAT   ENERGY   AND   FUELS 


TABLE  XLI. 

COMBUSTION  DATA  ON    VARIOUS  UNITS. 


Combustion  of 

Combus- 
tion Heat 
in  Cal. 

Combustion  Temperature  in 
Degrees  C. 

With  Pure 
Oxygen. 

With  the 
necessary 
air  Volume. 

With 
double  the 
air  Volume. 

Hydrogen  to  steam  
Carbon  (amorphous)    to   carbon 
dioxide  
Carbon   (amorphous)    to    carbon 
monoxide  
Wood  dried  at  120°  
Wood  ordinary  with  20  per  cent 
hygroscopic  water  

Of  1  unit 
(weight) 
28780 

8080 

2400 
3600 

2750 
6860 
Of  1  Liter 
6.0 
Of  1  Mol. 
191930 
313200 
68370 
125930 
773400 

Degrees 
6670 

10201 

Degrees 
2665 

2719 

1400 
2500 

1900 
2400 

2530 

2440 
2750 
3040 
2860 
2790 

Degrees 

1410 

1300 

1100 
1340 

Coke 

7500 

7160 
8620 
7180 
6940 

Illuminating  gas  

Methane  CH4  to  CO2  and  H2O 
Ethylene  C2  H4  to  CO2  and  H2O  .  . 
Carbon  monoxide  CO  to  CO2.".  .    . 
Water  gas  CO  +  H2  to  CO2  +  H2O 
Benzole  C6H6  to  CO2  and  H2O  ... 

If  the  combustion  of  fuel  and  air  takes  place  at  any  other 
temperature  than  0  degrees,  proper  allowances  must  be  made. 
If  we  had  to  burn,  for  instance,  1  kg.  of  hydrogen  of  50°  C.  with 
exactly  the  theoretical  amount  of  dry  air  of  20°  C.,  the  quantity 
of  heat  available  after  combustion  is  figured  as  follows : 


170.45     cal. 


34.88     cal. 


1  kg.  of  hydrogen  of  50°  C.  contains  1  X  3.409 

X  50 

8  kg.  of  oxygen  of  20°  C.  contain  8  X  0.217 

X  20 

26.64  kg.  of  nitrogen  (which  are  present  in  the 

combustion-air  besides  the  oxygen)  of 

20 degrees  contain  26.64  X  0.244  X  20. .  65.00     cal. 

Sum  of  the  heat  supplied  before  combustion .  .    =       270.33     cal. 
The  combustion  of  1  kg.  of  hydrogen  to  steam 

yields 

Heat  quantity  available  after  combustion.  ...    =  29,050.33     cal. 


28,780.00     cal. 


COMBUSTION-TEMPERATURE  131 

On  the  other  hand  the  heat  capacity  of  the  combustion  pro- 
ducts is  : 

Steam  (1  +  8)  X  0.4805  ..................  4.325  cal. 

Nitrogen  26.64  X  0.244  ...................    -  6.500  cal. 

Total  ...............................  10.825  cal. 

The  temperature  of  combustion  therefore  is  : 
29,050.33 


If  the  temperature  of  hydrogen  and  air  before  combustion 
had  been  0°  C.,  the  temperature  of  combustion  (according  to 
Table  XLI)  would  have  been  2665  degrees.  The  heating  of 
the  hydrogen  to  50  degrees  and  of  the  air  to  20  degrees  therefore 
increases  the  temperature  of  combustion  by  2683  -  2665  =  18°  C. 

The  results  of  these  methods  of  calculation  are  too  high,  as 
the  specific  heat  of  substances  increases  considerably  with  the 
temperature.  The  law  governing  the  relations  of  specific  heat 
and  temperature  (for  gases)  can  be  expressed  according  to  Le 
Chatelier  'by  one  of  the  general  equations 

Cp  =  6.5  +  aT 
or  Cv  =  4.5  +  aT. 

CP  and  Cv  stand  for  the  average  specific  heat  of  1  gram- 
molecule  at  constant  pressure  or  constant  volume  respectively, 
T  is  the  absolute  temperature,  a  has  the  following  values  for 
different  gases  : 

for  2  atomic  gases  (H2,  N2,  02,  CO)  .......  a  =  0.0006 

for  CO2  ...............................  a  =  0.0037 

for  H20  ...............................  a  =  0.0029 

for  C2H4  ......  ........................  a  =  0.0068 

The  total  heat  content  of  a  gas  at  the  temperature  T  =  CPXT 
or  Cv  X  T  and  the  difference  of  the  heat  content  of  a  gas  between 
T  and  T0  is  Cp  (T  -  T0)  and  Cv  (T  -  T0)  respectively. 

For  simplifying  the  calculation  the  following  table  gives  the 
values  of  Cp  (T  -  T9),  also  the  difference  (Cp  -  Cv)  (T  -  T0) 
=  A  X  P  (V  -V0)  =  nAR  (T  -  T0),  i.e.  the  external  work 
according  to  H.  Le  Chatelier. 


132 


HEAT  ENERGY  AND  FUELS 


TABLE  XLII. 

DATA  ON  EXTERNAL  WORK. 


Temperature  °  C. 

0 

200 

1.4 
1.8 
1.9 

0.4 

400 

2.8 
3.7 
4.0 

0.8 

600 

4.3 
6.0 
6.4 

1.2 

800 

5.8 
8.2 
9.0 

1.6 

1000 

1200 

1400 

1600 

CO,  N2,  O2,  H2.. 
HO 

0 
0 
0 

0 

7.4 
11.0 
12.4 

2.0 

9.0 
14.0 
15.5 

2.4 

10.7 
17.0 
19.2 

2.8 

12.5 
20.3 
23.1 

3.2 

CO2 

Work 

AR(T-T0)  

Temperature  °  C. 

1800 

2000 

2200 

2400 

2600 

2800 

3000 

CO,  N2,  02,  H2  
H20  
CO2  
Work 
AR(T  —  T0)  

14.2 
24.0 
27.3 

3.6 

16.0 

28.3 
32.0 

4.0 

17.3 
32.5 
38.2 

4.4 

19.1 
36.8 
43.7 

4.8 

21.0 
41.5 
49.6 

5.2 

22.9 
46.4 
55.4 

5.6 

24.8 
51.3 
61.7 

6.0 

EXAMPLE:    Calculation  of  the  combustion  heat  of  hydrogen 
in  air.     Pure  dry  air  contains  in  100  mols. 

20.8  02  +  79.2  Nv  or  about 
20  02  +  80  Nv  or  about  4  mols.  N  for  every  mol.  0. 

The  combustion  of  hydrogen  with  the  theoretical  amount  of 
air  therefore  corresponds  to  the  equation  : 


In  this  equation  we  have  at  constant  pressure  a  combustion  heat 
of  58.2  cal.  =  58,200  cal.  for  every  mol.  of  burned  hydrogen. 
The  products  of  combustion  consist  of  1  mol.  steam  (H20)  and 
1  mol.  nitrogen.  Since  the  combustion  heat  is  equal  to  the 
cooling  heat,  we  have  : 

58,200  =  6.5  (T  -  T0)  +  0.0029  (T2  -  T02)  +  2  [6.5  (T  -  T0) 
+  0.0006  (T2  -  TQ2)]  =  19.5  (T  -  T0)  +  0.0041  (T2  -  T02). 

If  TO  =  0°  C.  and  x  the  temperature  (in  °  C.)  to  be  found,  we 
have 

T0  =  273    and     T  =  273  +  x    and 
58,200  =  19.5  x  +  0.0041  (546  x  +  x2). 


COMBUSTION-TEMPERATURE 


133 


This  is  a  quadratic  equation  the  solution  of  which  is  not  at 
all  difficult,  but  most  conveniently  obtained  by  graphical  con- 
struction. We  know  that  the  combustion-temperature  is  in 
the  neighborhood  of  2000°  C.  Calculating  the  cooling  heats  for 
temperatures  in  this  neighborhood  we  have,  using  Table  XLI : 


1800° 

2000°  C. 

2200°  C. 

2400°  G. 

H2O..  . 

24  0 

28  3 

32  5 

36  8 

2N2  

28  4 

32  0 

34  6 

38  2 

Total  

52.4 

60.3 

67.1 

75.0 

The  combustion  temperature  in  question  therefore  must  be 
between  1800  and  2000°  C.  By  taking  the  cooling-heats  as  ordi- 
nates  and  the  temperatures  as  abscissas  we  obtain  the  curve 
shown  in  Fig.  30.  By  marking  on  the  ordinate-axis  the  heat- 


FIG.  30.  —  Diagram  for  Combustion  Temperatures. 


generation  (58.2  cal.)  drawing  from  here  a  horizontal  line  to  its 
intersection  with  the  curve,  and  a  vertical  line  through  the 
intersection  point,  we  see  that  the  vertical  line  intersects  the 
axis  of  temperature  at  a  point  corresponding  to  the  required 
combustion-temperature  (1960°C.).  An  analogous  calculation 
is  applied  if  the  combustion  takes  place  at  constant  volume  (for 
instance,  in  Mahler's  bomb) .  The  combustion  heat  at  constant 
volume  (taking  the  water  as  steam)  is  58  calories.  The  heat 


134 


HEAT   ENERGY   AND  FUELS 


necessary  for  heating  is  obtained  by  deducting  the  external 
work  3  AR  (T  -  770) : 


1800° 

2000° 

2200° 

2400° 

Heat  required  at  constant  pressure 
External  work  

52.4 
10.8 

60.3 
12.0 

67.1 
13.2 

75.0 
14.4 

Difference 

41  6 

48   3 

KQ  q 

fin  fi 

From  Fig.  31  we  see  that  the  combustion-temperature  is  2320°  C. 
In  this  calculation  the  dissociation  is  not  considered;  therefore 


so. 


iooo° 


2200" 


606 


2320 


„   VOP 


FIG.  31.  —  Diagram  for  Combustion  Temperatures. 

the  calculated  temperatures  are  slightly  too  high.  The  dis- 
sociation however  can  be  taken  into  consideration  by  inserting 
in  the  temperature  equation  the  coefficient  of  dissociation  as  a 
function  of  the  temperature.  Generally,  however,  a  different 
method  is  pursued. 

As  an  example  we  will  discuss  the  combustion  of  carbon 
monoxide.  Calculating  the  combustion-temperature  without 
considering  the  dissociation,  we  find  as  the  result  2100°  C.  We 
know  from  the  preceding  chapter  that  the  coefficient  of  dissocia- 
tion of  carbon  dioxide  at  this  temperature  and  at  a  partial 
pressure  of  0.20  atm.  is  0.06.  The  heat-generation  resulting 
from  combustion  therefore  is  68  (1  -  0.06)  =  64  cal. 


COMBUSTION-TEMPERATURE  135 

In  calculating  the  cooling-heat  of  the  combustion-products 
we  have  to  take  0.06  less  C02  (the  amount  dissociated  at  this 
temperature),  and  we  have  to  add  0.06  CO  +  0.03  02,  whereby 
the  heat  required  for  heating  is  decreased  by 

0.06  (33.8  -  1.5  X  16.6)  =  0.6  X  8.9  =  5.34  cal. 

The  heat  of  combustion  is  therefore  2050  instead  of 
2100°  C. 

Analogous  calculations  show  the  following  values  for  the 
combustion-temperature  of  different  gases  with  air  containing 
20  per  cent  of  oxygen  at  an  initial  temperature  of  0°  C.,  without 
considering  the  dissociation: 

TABLE   XLIII. 
COMBUSTION-TEMPERATURE  OF   VARIOUS  GASES. 


At  Constant 

Pressure. 

Volume. 

H2.. 

I9600  C 
2100°  C 
2040°  C 
1850°  C 
1525°  C 

2320°  C 
2430°  C 
2370°  C 
2150°  C 
I8600  C 

CO  

k  (CO  +  H,) 

CH4  to  CO2  +  2H2O  
CH4  to  CO  +  2H2O  

By  comparing  these  with  the  previously  calculated  tempera- 
tures of  combustion  (which  were  obtained  by  assuming  the 
specific  heats  to  be  constant)  the  excess  of  the  latter  can  be  noted. 

COMBUSTION-TEMPERATURE  OF  SOLID  SUBSTANCES. 

The  same  method  of  calculation  can  be  applied  to  the  com- 
bustion of  solid  substances  as  carbon,  coals,  etc.  We  suppose 
again  the  air  to  contain  20  per  cent  volume  of  oxygen.  For  sim- 
plifying the  calculation  such  quantities  of  the  solid  fuel  are  used 
that  the  volume  of  the  gases  of  combustion  (reduced  to  0°  C.  and 
760  mm.  pressure)  is  22.42  liters,  i.e.  corresponds  to  a  mol., 
because  the  volumetric  composition  of  the  combustion  gases 
then  shows  directly  the  number  of  mols  of  the  different  gas- 
constituents  present. 


136  HEAT  ENERGY  AND  FUELS 

We  will  now  consider  the  combustion  heat  of  amorphous 
carbon,  which  differs  from  that  of  diamond  or  graphite. 

12  g.  diamond  yields 94.3  cal. 

12  g.  graphite  yields 94.8  cal. 

12  g.  amorph.  carbon  yields 97.6  cal. 

According  to  the  equation 

C  +02  +4N2  =  C02  +4N2; 
the  composition  of  the  combustion  gases  is : 

C02 20  per  cent  volume 

N2 80  per  cent  volume 

In  order  to  obtain  a  molecular  volume  (22.42  liters)  of  com- 
bustion-gases 0.2  gram-atoms  of  carbon  must  be  burned,  which 
yields  by  the  combustion : 

Q  =  0.20  X  97.6  =  19.5  cal. 
The  heating  of  the  combustion-products  requires : 


2000°  C. 

2200°  C. 

For  CO2  

6  40 

7  64 

For  4N2  

12  80 

13  84 

Total     .... 

19.20 

21.48 

The  combustion-temperature  in  question  therefore  is  2026°  C. 
Actually,  however,  not  only  C02  is  formed  by  the  combustion, 
but  also,  according  to  circumstances,  either  free  oxygen  (dis- 
sociation), or  carbon  monoxide  or  steam  (from  hygroscopic 
water).  Accordingly  we  get  the  following  results: 

COMBUSTION  OF  AMORPHOUS  COAL. 

Theoretically,  if  C02  is  formed  exclusively. . .  2026°  C. 

With  5  per  cent  oxygen 1950°  C. 

With  5  per  cent  carbon  monoxide 1930°  C. 

Theoretically,  with  25  g.  of  water  per  1  kg. 

carbon... 1950°  C. 

Combustion  to  carbon  monoxide 1250°  C. 


COMBUSTION-TEMPERATURE  137 

COMBUSTION-TEMPERATURE  OF  A  NATURAL  COAL. 

The  combustion-temperature  of  a  natural  coal  is  figured  by  a 
similar  method.  As  an  example  we  take  bituminous  coal  of 
Commentry  showing  the  following  composition : 

C 75.2  per  cent 

H 5.2  per  cent 

0 ~ 8.2  per  cent 

N 1.0  per  cent 

Hygrosc.  H20 3.4  per  cent 

Ash 7.0  per  cent 

Total 100.0  per  cent 

The  composition  of  the  combustion  gases  is  calculated  as 
follows : 

C02  =  752  :  12  = 62.7  (1) 

H20  hygroscopic  =    34  :  18  = 1.9  >   ~7  q          ~v 

from  coal  =    52  :    2  = 26.0  \  ' 

N :  By  the  combustion  there  are  formed : 

C02with 62.70 

H20  with 13.00 

Total 75.70 

From  the  coal 2.50 

Difference 73.20 

This  73.2  0  corresponds  to 

4X73.2= 292.8N) 

N  from  coal  10  :  28  = 0.4  Np 

Total  from  (1),  (2),  (3) 383.8  volume. 

,  The  volumetric  composition  of  the  combustion-gases  therefore 


is: 


CO,  10°38X3  g2"7  =  16.34  per  cent  voL 


.    7.27  per  cent  vol. 

XT     100  X  293.2 

N     —  -  =  76.39  per  cent  vol. 

ooo.o 
Total  ......     100.00  per  cent  vol. 


138 


HEAT  ENERGY  AND  FUELS 


From  this  we  can  figure  the  heat  of  the  combustion  gases  : 

1800°  C.  2000°  C.  2200°  C. 

17.053  19.508  21.820 

The  combustion  heat  is 

Q  =  19.888  cal. 
and  the  combustion-temperature  2034°  C. 

COMBUSTION-TEMPERATURE  OF  PRODUCER  GAS. 

As  we  shall  see  later  there  are  frequently  used  in  the  industries 
gaseous  fuels,  which  allow  a  better  utilization  of  heat.  The 
ideal  composition  of  such  a  producer  gas  is  : 

CO  +  2  N2. 
Theoretically,  this  gas  requires  for  combustion 

i(02)  +2N2 
and  yields 


C0 


4  N2. 


The  combustion  of  CO  +  }  (02)  +  4  N2  gives  68  cal. 

If  the  gas  is  heated  before  combustion  to  1000°  C.,  5.5  X  7.3 
=  40  cal.  are  required.  The  total  amount  of  heat,  therefore,  on 
which  the  calculation  of  the  combustion-temperature  has  to  be 
based  is  68  +  40  =  108  cal. 

TABLE   XLIV. 

HEAT    OF    THE    COMBUSTION    PRODUCTS 


2000°. 

2200°  C. 

2400°  C. 

CO2.. 

4N, 

32.0 
64  0 

38.2 
69  2 

43.7 
76  4 

Total     

96  0 

107  4 

120  1 

Combustion-temperature  =  2220°  C. 

,    The  same  gas  gives  under  different  conditions : 

Theoretically,  cold 1500°  C.;  cold,  5  per  cent  0    1210°  C. 

Gas  +  air    500° I8600  C.;  cold,  5  per  cent  CO  1320°  C. 

Gas  +  air,  1000° 2220°  C. 


COMBUSTION-TEMPERATURE  139 

The  air  used  for  the  production  of  producer  gas  always  contains 
varying  quantities  of  water  vapor  or  steam,  which  is  decom- 
posed by  coming  in  contact  with  glowing  coal,  so  that  the  gas 
contains  less  nitrogen.  With  an  average  content  of  250  g.  of 
water  per  kilogram  of  coal,  the  gas  obtained  contains  per  gram- 
atom  of  carbon : 

CO  +  t  (H2)  +  4  (N2). 

The  combustion-temperature  of  this  gas  is : 

Gas  +  air:  cold 1550°  C. 

Gas  +  air:  500° 1930°  C. 

Gas  +  air:  1000° 2230° C. 

In  practice  however  the  composition  of  producer  gas  differs 
from  the  above,  since  it  always  contains  some  C02  and  H20  and 
also  (if  bituminous  coal  or  lignite  is  used)  gaseous  hydrocarbons. 
As  an  example  the  following  analysis  of  such  a  gas  is  given 
(referred  to  1  mol.  of  gas  mixture) : 

CO 0.20  vol. 

H2....- 0.10vol. 

C02 0.05  vol. 

H20 0.02  vol. 

N 0.63  vol. 

Total 1.00vol. 

The  combustion  of  this  gas  yields : 

TABLE   XLV. 
COMBUSTION  OF  PRODUCER  GAS. 


Combustion  Products. 

Combustion  Heat. 

CO2         .  .                        0  25 

13  6  cal 

H2O.      ...                   0  12 

5  8  cal 

N2  1  23 

Total  1.60 

19.  4  cal. 

The  calculation  shows  the  following  combustion-temperature: 

Gas  and  air:  cold 1350°  C. 

Gas  and  air:  1000°. .  .  2150°  C. 


140  HEAT  ENERGY  AND  FUELS 

SUGGESTIONS  FOR  LESSONS. 

Calculation  of  the  combustion-temperature  of  a  fuel  of  known 
composition  and  combustion  heat,  using  different  quantities  of 
combustion  air,  at  different  temperatures  of  fuel  and  air. 

Calculation  of  the  combustion-temperature  if  the  composition 
of  the  combustion  gases  (at  different  temperature  of  fuel  and  air) 
is  given,  besides  the  composition  and  the  thermal  value  of  the 
fuel. 


CHAPTER  VIII. 


FUELS.     (IN   GENERAL.) 

WE  call  "fuel"  any  substance  which  combines  with  oxygen 
accompanied  by  the  generation  of  heat  and  therefore  can  be 
used  in  practice  as  a  source  of  power. 

Under  the  term  "fuel"  in  the  widest  sense  of  the  word  we 
include  solids  and  liquids  containing  carbon  (wood,  peat,  coal, 
coke,  oil,  tar,  alcohol,  etc.)  and  gases  containing  carbon  or  hydro- 
gen (illuminating  gas,  natural  gas,  producer  gas,  water  gas,  etc.) 
and  also  various  other  substances,  the  oxidation  of  which  is  used 
in  the  industries  as  a  source  of  heat.  Some  of  the  latter  sub- 
stances are : 

Sulphur,  which  is  used  in  southern  Italy  for  smelting  crude 
sulphur  (the  reason  being  that  no  other  fuel  can  be  obtained 
as  cheaply). 

Sulphides  (FeS2)  are  used  as  fuel  in  the  roasting  of  ore.  In 
the  Bessemer  process  the  silicon  of  the  crude  iron  (acid  process) 
or  the  phosphorous  (basic  process)  is  used  as  fuel. 

TABLE  XL VI. 
CLASSIFICATION  OF  FUELS. 


Kind  of  Fuel. 

a)  Natural. 

b)  Artificial. 

A.    Solid  

Wood,  peat  lignite  bi- 

Charcoal      coke      (bri- 

B.  Liquid   
C.  Gaseous  

tum,  coal,  anthracite. 
Oil  
Natural  gas 

quettes). 
Tar,  tar  oil,  alcohol,  etc. 
Illuminating    gas     pro- 

ducer gas,   water  gas, 
Dowson       gas,       blast 
furnace  gas,  acetylene, 
etc. 

141 


142 


HEAT  ENERGY  AND  FUELS 


Lately  Goldschmidt  has  introduced  aluminium  as  a  fuel  (ther- 
mit). A  mixture  of  fine-grained  aluminium  and  certain  oxides 
(Fe203,  etc.),  when  ignited,  continues  to  burn  and  generates 
considerable  heat:  Fe2O3  +  2  Al  =  A1203  +  2  Fe.  This  process 
is  used  for  the  reduction  of  metals,  preparation  of  metals  and 
alloys,  free  of  carbon,  generation  of  high  temperatures  for  weld- 
ing, melting,  casting,  etc. 

In  this  work  we  will  treat  only  the  first  two  groups  given 
above,  which  are  commonly  called  fuels  in  the  true  sense  of  the 
word. 

A.    SOLID  FUELS. 

(a)  Natural  Solid  Fuels,  Wood,  Peat,  Lignite,  Coal  and 
Anthracite. 

All  these  fuels  contain: 

1.  Ash,  which  remains  after  combustion. 

2.  Hygroscopic  water,  sometimes  called  moisture. 

3.  A  substance  containing  the  combustibles  and  consisting 
mainly  of  carbon  and  variable  quantities  of  hydrogen,  oxygen  and 
nitrogen.    The  composition  of  this  substance  free  of  water  and 
ash  is  as  follows  for  the  different  fuels : 

TABLE   XLVII. 

COMPOSITION  OF  FUELS. 


Composition  of  the  Sub- 

Vola- 

stance (free  of  Water  and 

Ther- 

tile 

Ashl 

mal 

Fuel. 

A&LL)  , 

Value. 

Coke. 

Mat- 

c% 

H% 

0  +  N% 

Cal. 

ters. 

Wood  

51 

6 

43 

4700 

non-coking  .  .  . 

Peat  

58 

6 

36 

5900 

non-coking  .  . 

"70  " 

Lignite  

70 

5 

25 

6500 

non-coking  .  .  . 

50 

Bitum.  coal: 

lean,  long    flam- 

ing   

80—84 

5.5 

12—10 

8200 

badly  coking.. 

35—40 

fat,  long  flaming 

84—88 

5 

9—10 

8600 

coking  

30—35 

fat,  short    flam- 

ing   

86—90 

5—4.5 

7—5.5 

8700 

coking  

16—23 

lean,  short  flam- 

ing   

90—93 

4.5—3.5 

5.5—4.5 

8600 

badly  coking  . 

6—14 

Anthracite  

95 

2 

3 

8200 

non  coking.  .  . 

3 

The  ash  content  varies  from  about  5  per  cent  to  15  per  cent. 
The  amount  of  hygroscopic  water  depends  on  the  humidity  of 


FUELS  143 

the  atmosphere,  and  the  nature  and  porosity  of  the  fuel;  it 
generally  increases  in  direct  proportion  with  the  volatile  matter. 
Coke  forms  an  exception  as  it  sometimes  contains  considerable 
water,  which  however  is  not  hygroscopic  but  was  introduced  by 
the  manufacturing  process  (cooling  of  the  hot  coke  with  water). 

The  coking  of  fuels  by  heating  is  of  great  practical  importance, 
preventing  small-size  coal  from  falling  through  the  grate  bars. 
Small-sized  lean  coal  is  troublesome  to  burn  on  a  grate.  On 
the  other  hand  coking  too  much  may  cause  trouble,  as  thereby 
a  considerable  amount  of  coal  is  prevented  from  burning  up  and 
the  grate  cannot  be  properly  cleaned. 

Some  lean  fuels  have  the  property  of  disintegrating  in  heat 
and  falling  through  the  grate  before  being  burned  up. 

The  natural  solid  fuels  are  of  great  importance  for  the  indus- 
tries on  account  of  their  low  cost.  They  can  be  classified  in 

(a)  Vegetable  fuels :  wood. 

(/?)  Fossile  fuels :  peat,  lignite,  coal  and  anthracite. 

(6)  Artificial  Solid  Fuels. 

For  certain  purposes  it  is  of  advantage  to  use  fuels  richer  in 
carbon  than  the  ones  occurring  in  nature.  This  is  done  by 
subjecting  the  natural  solid  fuels  to  dry  distillation,  whereby 
the  following  products  of  decomposition  are  formed : 

1.  Gases. 

2.  Tar. 

3.  Tar- water. 

4.  Carbonaceous  residuum. 

The  relative  quantity  of  these  substances  depends  on  the 
nature  of  the  substance  from  which  it  originated,  and  the  tem- 
perature of  distillation.  With  increasing  temperature  the  quan- 
tity of  gas  is  increased,  but  the  content  of  heavy  hydrocarbons 
and  therefore  the  illuminating  power  decreased. 

The  advantages  of  the  coked  fuel  are : 

1.   A  fuel  of  higher  thermal  value : 

(a)  The  content  of  carbon  of  the  coked  fuel  being  higher  than 

that  of  the  raw  fuel. 

(b)  The  gaseous  products  of  distillation  requiring  a  great 

amount  of  heat  for  their  gasification  in  using  crude 
fuel. 


144  HEAT  ENERGY  AND  FUELS 

Thereby  the  cost  of  transportation  per  heat  unit  is  decreased. 

2.  Coked  fuel  burns  without  smoke. 

3.  Coked  fuel  does  not  cake  or  form  clinkers. 

4.  The  sulphur  content  of  the  raw  fuel  is  decreased  by  coking. 

5.  Valuable  by-products  are  furnished  by  the  coking  process. 

On  the  other  hand  we  have  to  consider  the  following  disadvan- 
tages of  coking. 

1.  The  coking  entails  a  certain  expense  due  to  heat,  fuel, 
wages  and  machinery. 

2.  Coked  fuel  never  burns  with  a  long  flame,  which  is  essential 
in  certain  cases. 

3.  Coking  increases  the  ash  content. 

According  to  the  raw  material  used  the  coked  products  are 
called:  .- 

(a)  Charcoal. 

(6)  Peat  coal. 

(c)  Coke. 

(d)  Briquettes. 


CHAPTER  IX. 
WOOD. 

THE  industrial  importance  of  wood  as  fuel  is  not  very  great. 
It  is,  however,  used  to  a  large  extent  for  building  and  con- 
struction purposes  which  makes  a  detailed  discussion  desirable. 

According  to  the  trees  from  which  the  woods  originate  they 
may  be  classified  as: 

(a)  Leaved   woods:    maple,   birch,   beech,   oak,   alder,   ash, 
linden,  poplar,  elm,  willow,  etc. 

(b)  Coniferous  woods :  red  pine,  pine,  larch,  fir. 

TABLE  XLVIII. 

CLASSIFICATION  OF  WOODS  ACCORDING  TO  SPECIFIC  GRAVITY. 


Hard  Woods. 

Soft  Woods. 

Specific  Gravity  (air  dry) 
Specific  Gravity  (green) 

>0.55 
>0.90 

Specific  Gravity  (air  dry) 
Specific  Gravity  (green) 

<  0.55 
<  0.90 

Beech 
Oak 
Ash 
Maple 
Elm 
Birch 
Alder 

=  0.77 
=  0.71 
=  0.67 
=  0.64 
=  0.57 
=  0.55 
=  0.54 

Silver  fir 
Red  pine 
Fir 
Larch 
Linden 
Willow 
Trembling  poplar 
Poplar 
Black  poplar 

=  0.48 
=  0.47 
=  0.55 
=  0.47 
=  0.44 
=  0.48 
=  0.43 
=  0.39 
=  0.39 

The  specific  gravity  of  wood  is  somewhat  variable :  it  is  greater 
the  slower  the  growth  of  the  tree,  i.e.,  the  dryer  the  soil.  Some- 
times the  following  classification  is  used. 

1.  Hard  woods  (leaved  woods  only) :  oak,  beech,  white  beech, 
ash,  maple,  birch,  etc. 

2.  Soft  woods  (soft  leaved  woods) :  chestnut,  linden,  trem- 
bling poplar,  willow,  etc. 

3.  Coniferous  woods :  fir,  silver  fir,  etc. 

146 


146 


HEAT  ENERGY  AND  FUELS 


The  specific  gravities  given  above  include  the  pores  of  the 
wood.  Excluding  the  pores  these  figures  are  considerably 
higher  (Rumford).  See  Table  XLIX. 

TABLE   XLIX. 
SPECIFIC  GRAVITY  OF  WOOD   SUBSTANCE. 


Wood. 

Speci  fie 
Gravity. 

Wood. 

Specific 
Gravity. 

Oak 

1  5344 

Birch 

1   4848 

Beech 

1  5284 

Linden 

1  4846 

Elm 

1  5186 

F*ir          .                ... 

1  4612 

Poplar  

1  .  4854 

Maple  

1.4599 

The  following  figures  relative  to  specific  gravity  of  woods  will 

be  of  interest: 

TABLE  L. 

SPECIFIC  GRAVITY  OF   VARIOUS  WOODS. 


Kind  of  Tree. 

Bris- 
son. 

Hartig. 

Wernek. 

Winkler. 

Muschen- 
brock. 

Green. 

Seasoned. 

Well 
Seasoned. 

Well 

Seasoned. 

Scarlet  oak  
Beech  
Elm  

0.85 
0.67 

0.75 
0.84 

1.0754 
0.9822 
0.9476 
0.9250 
0.9121 
0.9036 
0.9036 
0.9012 
0.8993 
0.8941 
0.8699 
0.8633 
0.8614 
0.8571 
0.8170 
0.7795 
0.7654 
0.7634 
0.7155 

0.7075 
0.5907 
0.5474 
0.4735 
0.5502 
0.6592 
0.6440 
0.5550 
0.4716 
0.5910 
0.5749 
0.5001 
0.4390 
0.3656 
0.4302 
0.3931 
0.4302 
0.3931 
0.5289 

0.6441 
0.5452 
0.5788 

0.4205 
0.5779 
0.6337 
0.5699 

0*4303 
0.3838 

0.3480 
0^4402 

0.663 
0.560 
0.518 
0.441 
0.485 
0.618 
0.619 
0.598 
0.552 
0.493 
0.434 
0.549 

0*443 
0.431 
0.346 
0.418 

0^501 

0.929 
0.852 
0.600 

0^755 
0.734 

0^550 
0.874 

oisoo 

0.604 
0.383 

Larch  ' 
Pine  '....  
Maple 

Ash  
Birch  

Service  
Fir  

0.55 

Red  pine 

Mealy  pear  
Chestnut  
Alder  
Linden  

0.80 
0.60 

Black  poplar  

Aspen  
Italian  poplar  
Sallow  
Pomegranate  
Ebony  
Dutch  box  
Medlar  
Olive  
French  box  
Spanish  mulberry. 
Spanish  yew  

1.35 
1.33 
1.32 
0.94 
0.92 
0.91 
0.89 
0.80 







•  • 

WOOD 


147 


Another  classification  of  woods  is  based  on  the  following 
properties : 

The  youngest  wood  of  a  tree  trunk  is  called  sap-wood.  It 
contains  more  sap  and  is  lighter  in  color  than  the  older  wood. 
In  some  trees  the  older  wood  hardly  changes  (maple,  birch, 
white  beech,  etc.) ;  in  some  the  sap-wood  is  darker  and  dryer 
(linden,  red  pine,  fir  tree,  etc.) ;  in  some  trees  a  darker,  dryer 
and  stronger  wood  is  formed  in  the  course  of  time,  which  is  called 
heart-wood  (ebony,  walnut,  larch,  fir,  etc.). 

The  weight  of  wood  piles  is  of  more  importance  than  the 
specific  gravity.  The  net  cubic  contents  of  a  wood  pile  is  the 
volume  of  wood  substance  including  the  pores.  Its  weight  in 
kilograms  is  1000  times  the  specific  gravity  of  the  wood.  The 
gross  cubic  contents  of  a  pile  depends  upon  the  density  of  the 
pile  and  the  moisture  of  the  wood.  Furthermore,  the  density 
depends  upon  the  shape  and  form  of  the  pieces  of  wood  (cord 
wood,  stove  wood  and  brush  wood).  The  moisture  decreases 
with  the  length  of  time  the  wood  is  stored,  down  to  from  12  to 
13  per  cent.  The  actual  contents  of  the  wood  pile  is  the  volume 
of  wood  substance  in  a  certain  volume  of  wood  pile. 


TABLE    LI. 

ACTUAL  CONTENT  IN  PER  CENT  OF  DIFFERENT  WOODS. 


Kind  of  Wood. 


Mini- 
mum. 


Maxi- 
mum. 


Aver- 
age. 


Cord  wood  of  leaved  wood,  logwood  and  billet  wood 
of  coniferous  trees,  strong,  smooth  and  straight. . 

Cord  wood  of  leaved  and  coniferous  woods,  weak, 
smooth  and  straight 

Cord  wood  of  coniferous  woods,  strong  and  weak, 
knotty  and  crooked 

Stove  wood  of  leaved  wood,  strong,  smooth,  straight 

Cord  wood  of  leaved  wood,  strong  and  weak,  knotty 
and  crooked  

Stove  wood  of  leaved  and  coniferous  wood,  strong 
and  weak,  smooth  and  knotty,  straight  and 
crooked 

Brushwood  from  trunk,  coniferous  wood 

Brushwood  from  trunk,  leaved  wood 

Brushwood  from  branches,  coniferous  wood 

Brushwood  from  branches,  leaved  wood 

Rootwood  (leaved  and  coniferous  tree) 


73 

68 

63 


58 
53 
48 

42 


77 


72 


67 


62 
57 
52 

48 


75 


70 


65 


60 
55 
50 

45 


148 


HEAT  ENERGY  AND  FUELS 


TABLE  LII. 

WEIGHTS  OF  WOOD  IN   PILES. 

(Woods  cut  in  winter.) 


Kind  of  Tree. 

Green. 

Seasoned. 

Cord  wood. 

Stove- 
wood. 

Brush. 

Cord  wood. 

Stove- 
wood. 

Brush. 

Bark. 

Heart- 
wood. 

Bark. 

Heart- 
wood. 

Weight  in  Kilograms  of  1  Solid  Cubic  Meter. 

Red  pine  
Pine              

892 
950 

741 
790 

717 
690 

923 

878 

881 
937 
929 
937 
968 
955 
1019 

979 

926 
869 

'903 
930 
1045 
986 
781 

457 
554 

548 
687 

734 
741 

445 
503 

669 
734 

"797' 

334 
551 
624 
469 
703 
696 
762 

"717" 

511 
516 

702 
673 
780 
712 
484 

Larch  
Silver  fir  

Oak  

Red  beech 

Hornbeam 

Birch  
Linden  
Maple  
Norway  maple  

978 
1051 

933 

CHEMICAL  COMPOSITION. 

Wood  is  composed  chemically  of  (1)  fiber  and  (2)  sap. 

The  wood  fiber  consists  mainly  of  cellulose  C6H1005  (C,  44.44 
per  cent;  H,  6.17  per  cent;  0,  49.39  per  cent).  Besides  cellulose 
we  find  other  organic  matter,  both  nitrogenous  and  non-nitroge- 
nous, which  are  generally  called  "incrustating  materials. "  They 
increase  towards  the  center  and  cause  the  dark  color. 

The  analyses  given  in  .Table  LIII  show  the  variations  in  the 
composition  of  different  woods  dry  and  free  of  ash:  (H.  Che- 
vandier). 

TABLE  LIII. 
COMPOSITION  OF  DIFFERENT  WOODS. 


Kind  of  Tree. 

C 
Per  cent. 

H 
Per  cent. 

OandN 
Per  cent. 

Maple  
Oak  

49.80 
50  64 

6.31 
6  03 

43.89 
42.05       1  28 

Pine  .... 

49  94 

6  25 

43  81 

Willow  . 

51  75 

6  19 

41  08      0  98 

WOOD 


149 


The  average  composition  therefore  is : 


C 

H 

O  and  N 


49.2 

6.1 

44.7 


The  sap  is  a  solution  of  various  organic  (protein,  tannic  acid, 
vegetable  acids,  starch,  sugar,  essential  oils,  resins)  and  inorganic 
substances  in  water. 

Considering  the  use  of  wood  as  fuel,  only  the  content  of  resin, 
water  and  ash  has  to  be  considered. 

With  increasing  content  of  resin,  the  thermal  value  increases. 

In  order  to  determine  the  resin  content  Hampel  treated 
Austrian  woods  with  90  per  cent  alcohol.  Table  LIV  gives  the 
per  cents  dissolved. 

TABLE  LIV. 
RESIN  CONTENT  OF  WOODS. 


Kind  of  Tree. 


Taxus  baccata  L.  (yew)  
Abies  excelsa  E)  C   (fir)                  

i 

r.5i4 

J.734 

Larix  europflBa  D  C    (larch)     

.807 

744 

Acer  pseudoplatanus  L    (maple) 

69 

Fraxinus  excelsior  L  (ash) 

47 

Fajrus  silvaticus  L    (red  beech) 

44 

Betula  alba  L  (birch) 

167 

Per  cent. 


The  ash  content  of  various  woods  may  be  taken  from  Table 
LV. 

TABLE  LV. 
ASH  CONTENT  OF  VARIOUS  WOODS. 


Fresh 

Old 

Trunk 

Branch 

Brush 

Wood. 

Wood. 

Wood. 

Wood. 

Wood. 

Pine  

0.12 

0.15 

Oak  

1.94 

1.49 

1.32 

Oak  

0.15 

0.11 

Beech  

0.73 

1.54 

0.72 

Pitch  pine  . 

0.15 

0.15 

Aspen  

1.49 

2.38 

Birch  

0.25 

0.30 

Willow.... 

2.94 

3.66 

The  ash  content  depends  largely  on  the  ash  content  of  the 
soil.  The  moisture  changes  with  the  seasons,  is  the  lowest  in 
winter  and  the  highest  in  spring.  It  also  changes  with  the 
different  trees. 


150 


HEAT   ENERGY  AND  FUELS 


Kind  of  Tree. 

H2O 
Per  cent. 

English 
Name. 

Carpinus  betulus  
Salix  caprea  

18.6 
26  0 

Hornbeam 
Sallow 

Acer  pseudoplatanus  
Sorb  us  aucuparia.  .    . 

27.0 
28  3 

Maple 

Fraxinus  excelsior  

28  7 

Ash 

Betula  alba  . 

Qf)     0 

"RirpVi 

Quercus  robur  

34  7 

Oak 

Pinus  silvestris  

39  7 

Pinp 

Pinus  larix  

48  6 

TABLE  LVI. 
MOISTURE  IN   VARIOUS  WOODS. 


Kind  of  Tree. 


Hornbeam  (Carpinus  betulus) . . 

Sallow  (Salix  caprea) 

Maple  (Acer  pseudoplatanus)  . . 
Service  tree  (Sorbus  aucuparia) 

Ash  (Fraxinus  excelsior) 

Birch  (Betula  alba) 

Oak  (Quercus  robur) 

Pine  (Pinus  silvestris,  L.) 

Larch  (Pinus  larix) 


Water 
Content. 


18.6 
26.0 
27.0 
28.3 
28.7 
30.8 
34.7 
39.7 
48.6 


The  researches  of  Vrolle  (Table  LVII)  show  how  great  are  the 
variations  in  the  ash  content,  for  instance,  in  the  case  of  the 
cherry  tree. 

TABLE  LVII. 
ASH  CONTENT  OF  VARIOUS  PARTS  OF  A  CHERRY  TREE. 


Part  of  Tree. 

C 
Per  cent. 

H 
Per  cent. 

0  +  N 
Per  cent. 

Ash 
Per  cent. 

Leaves.  .  . 

45  015 

6  971 

40  910 

7  ug 

Upper  point  of  branch,  bark  
Upper  point  of  branch,  wood  

52.496 
48.359 

7.312 
6.605 

36.637 
44.730 

3.454 
0  304 

Middle  part  of  branch,  bark  
Middle  part  of  branch,  wood  
Lower  part  of  branch,  bark  
Lower  part  of  branch,  wood  
Trunk,  bark 

48.855 
49.902 
46.871 
48.003 
46  267 

6.342 
6.607 
5.570 
6.472 
5  930 

41.121 
43.356 
44.656 
45.170 
44  755 

3.682 
0.134 
2.903 
0.354 
2  657 

Trunk,  wood  .  .  . 

48  925 

6  460 

44  319 

0  296 

Upper  part  of  root  bark  . 

49  085 

6  024 

48  761 

1   129 

Upper  part  of  root,  wood  
Middle  part  of  root,  bark  
Middle  part  of  root,  wood  
Lower  part  of  root  

49.324 
50.367 
47.399 
45.063 

6.286 
6.069 
6.259 
5.036 

44.108 
41.920 
46.126 
43.503 

0.231 
1.643 
0.223 
5.007 

WOOD 


151 


Henneberg's  researches  show  how  the  ash  content  depends  on 
the  soil.    Table  LVIII  shows  the  composition  of  beech  wood 

ash: 

TABLE  LVIII. 

ASH  ANALYSES. 


Kind  of  Soil. 

Components. 

Limestone. 
Per  cent. 

Gypsum. 
Per  cent. 

Sandstone. 
Per  cent. 

Carbonate  of  potash 

6  7  ) 

(  4.7 

Carbonate  of  soda 

11  0  J 

14.6 

J3.2 

Sulphate  of  potash 

4  4 

3  4 

23.3 

Chloride  of  sodium                      .... 

0  7 

trace 

5.0 

Soluble  salts                         .       .    . 

22  8 

18.0 

36.2 

Carbonate  of  lime  

27  4 

30.9 

21.1 

Magnesia  :  
Phosphates  
Silicic  acid 

17.7 
15.6 
16  9 

12.2 
9.7 

28  7 

12.4 
10.9 
18,4 

Insoluble  components  

77.6 

81.5 

61.0 

For  metallurgical  purposes  the  quantity  of  phosphorus  in  wood 
is  of  interest.     R.  Akerman  and  Sarnstrom  found  that : 

1.  Leaved  wood  contains  from  4  to  5  times  as  much  phos- 
phorus as  coniferous  trees. 

2.  The  quantity  of  phosphorus  in  the  same  kind  of  wood 
varies  100  per  cent  according  to  the  country  of  origin. 

3.  Fir  wood  cut  in  winter  contains  more  phosphorus  than 
when  cut  in  spring  or  summer. 

4.  The  trunk  contains  the  least,  branches,  twigs  and  especially 
the  bark  contain  the  most. 

5.  The  phosphorus  of  sap-wood  can  to  a  large  extent  easily  be 
washed  out. 

The  moisture  of  wood  depends  considerably  on  the  season 
(Schuebler) : 

Percentage  of  Water. 


jvina  01  iree. 

End  of  January. 

Beginning  of 
April. 

Ash  .  . 

28  8 

38  6 

Maple. 

33  6 

40  3 

Horse  chestnut  .  . 

40  2 

47  1 

Fir  tree  ' 

52  7 

61  6 

Fresh  ash  

28-29 

38-39 

Red  pine  (root)  

52 

61 

152 


HEAT  ENERGY  AND  FUELS 


The  moisture  varies  in  the  different  parts  of  the  trees.  It  is 
higher  in  the  outer  parts  than  in  the  inner  parts,  higher  in  the 
branches  than  in  the  trunk.  It  also  depends  on  the  soil  and 
climatic  conditions. 

Air  drying  reduces  the  moisture  after  two  summers  to  about 
20  per  cent,  in  very  dry  summers  to  from  15  to  16  per  cent. 

For  drying  wood  more  perfectly  higher  temperatures  have  to 
be  applied.  Woods  exposed  for  two  years  to  125°  C.  and  225°  C. 
lost  water  as  shown  in  Table  LIX.  (Violette) : 

TABLE  LIX. 

DATA  ON  THE   SEASONING  OF  WOOD. 


100  Parts  of  Wood  give  off  Water. 

Temperature. 

Oak. 

Ash. 

Elm. 

Walnut. 

125°  C 

15.26 

14.78 

15.32 

15.55 

150°  C 

17.93 

16.19 

17.02 

17.43 

175°  C 

32.13 

21'.  22 

36.94 

21.00 

200°  C 

35.80 

27.51 

33.38 

41.77 

225°  C 

44.31 

33.38 

40.56 

36.56 

At  200°  C.  dry  distillation  begins.  Wood  dried  at  higher 
temperature  reaclily  absorbs  water.  Wood  (shavings)  dried  at 
136°  C.  absorbed  in  24  hours  in  winter  from  17  to  19  per  cent,  in 
summer  from  6  to  9  per  cent  water. 

By  drying,  the  volume  is  decreased;  by  moistening,  increased. 

TABLE  LX. 
THERMAL  VALUE  OF  VARIOUS  WOODS   (per  kg.) . 


Kind  of  Wood. 

Pb  reduced 
by  1  Part  of 
Wood. 

Calories. 

Specific 
Gravity. 

\ir-dried  wood  (20%  water) 

3600 

Dried  wood  (10%  water) 

4100 

White  beech  air  dried.                 ..    . 

12  5 

3100 

0.770 

Oak,  air  dried.       

14.05 

2400—3000 

0.708 

Maple,  air  dried  

14.16 

3600 

0.645 

Pine  air  dried 

13  27 

0.550 

Willow  air  dried 

13  10 

0.487 

Linden,  air  dried                            .... 

14.48 

3400—4000 

0.439 

Birch,  air  dried  

14.08 

0.627 

Fir  tree  air  dried 

13  86 

0.481 

The  heat  of  combustion  of  cellulose  per  kilogram  is  as  follows, 
(if  the  water  formed  appears  in  liquid  form)  for: 


WOOD 


153 


Purified  cotton 4200     cal. 

From  paper .  4188.1  cal. 

From  ammoniacal  solution  of  cupric  oxide  4174.1  cal. 
Purified  with  bromine  water  and  ammonia .   4191.9  cal. 

Average . 4188.5  cal. 

For  water  vapor 3591     cal. 

Boise  has  found  the  evaporating  power  of  different  kinds  of 
wood  to  be  as  given  in  Table  LXI. 

TABLE   LXI. 
EVAPORATING   POWER  OF  WOOD. 


Kind  of  Tree. 

Water. 

Ash. 

Kilograms  of  Water 
transformed  into 
Steam  by  1  Kilo- 
gram of  Wood. 

Unseasoned. 

Seasoned. 

Unseasoned. 

Seasoned. 

Per  cent. 

Wood. 

Old  pine  . 

16.1 
19.3 
14.7 
12.3 
18.7 
22.2 
14.3 
12.5 

1.92 
1.73 
0.95 
1.00 
1.13 
1.43 
1.39 
2.17 

2.29 
2.15 
1.11 
1.14 
1.39 
1.84 
1.62 
2.48 

4.18 
3.62  - 
3.84 
3.72 
3.54 
3.39 
3.49 
3.62 

5.11 

4.77 
4.67 
4.39 
4.60 
4.63 
4.25 
4.28 

Young  pine  
Alder  

Birch 

Oak  
Old  red  beech  
Young  red  beech  
White  beech  

Winkler  has  found  the  comparative  fuel  value  of  woods, 
considering  the  same  volume,  to  be  as  given  in  Table  LXII. 

TABLE  LXII. 
COMPARATIVE  FUEL  VALUE  OF  VARIOUS  WOODS  (Winkler). 


Kind  of  Wood  (dry). 

Red  Pine 
=  100. 

Red  Beech 
=  100. 

Oak 

169 

118 

Elm 

156 

109 

Maple  ... 

153 

106 

Birch  

152 

105 

Beech  

143 

100 

Fir  

112 

78 

Willow  

110 

77 

Poplar  ... 

109 

76 

Pine  .                             

106 

74 

Red  pine  

100 

70 

Linden  

92 

64 

154  HEAT  ENERGY  AND  FUELS 

Since  wood,  when  used  as  fuel,  is  almost  always  measured 
instead  of  weighed,  this  table  is  of  considerable  importance,  also 
on  account  of  the  volume  being  less  affected  by  moisture  than 
the  weight. 

If  we  call  best  beech  wood  equal  to  100  we  get  the  following 
scale  for  the  value  of  woods. 

I.   Fuel  quality  =  100:   beech,  birch,  pine   rich   in  resin, 
mountain  pine,  acacia. 

II.   Fuel  quality  =  95  to  90:  maple,  elm,  ash,  larch  rich  in 
resin,  chestnut,  ordinary  pine. 

III.  Fuel  quality  =  85  to  75:  red  pine,  fir,  Siberian  stone 
pine. 

IV.  Fuel  quality  =  70 :  linden. 

V.   Fuel  quality  =  65  to  60 :  alder,  poplar,  oak,  aspen. 
VI.   Fuel  quality  =  55  to.  50:  willow. 

These  values  naturally  depend  also  on  the  use  the  wood  is  to 
be  put  to.  For  quickly  raising  the  temperature,  for  instance, 
soft  wood,  especially  coniferous  wood  is  used.  For  domestic 
use  1.5  cu.  m.  of  soft  wood  take  the  place  of  1  cu.  m.  of  hard 
wood. 

The  different  parts  of  a  tree  have  a  different  fuel  quality. 
Taking  trunk  wood  as  =  1,  we  have 

Trunk  wood 0.90  to  0.80 

Branch  wood 0.90  to  0.75 

Twig  wood  0.85  to  0.80 

Root  wood 0.65  to  0.50 

Root  wood,  rotten 0.40 

Wind-fallen  wood.  .  .  0.85  to  0.50 


CHAPTER  X. 
FOSSIL   SOLID   FUELS.     (IN   GENERAL.) 

ALL  fuels  containing  carbon  are  of  vegetable  origin  and  differ 
from  each  other  according  to  the  kind  of  the  plant  from  which 
they  come  and  the  quality  and  quantity  of  the  transformation 
of  the  vegetable  fiber.  The  course  of  carbonification  is  entirely 
different  if  the  vegetable  masses  are  covered  with  water,  and  if 
the  plants  are  isolated  from  the  atmosphere  by  layers  of  clay. 

Geologically  these  fuels  can  be  divided  in: 

1.  Younger  fossil  coals : 

(a)  Peat. 

(b)  Brown  coal  (lignite). 

2.  Older  fossil  coals  (bituminous  coal  and  anthracite) .     These 
coals  are  formed    by  a  process  called  natural  carbonification 
(carbonaceous  decomposition),  which  was  studied  by  the  Swiss 
geologist,  A.  Balzer. 

Balzer  states  that  in  this  process  two  kinds  of  substances  have 
to  be  dealt  with,  namely :  products  of  decomposition  and  resid- 
uum of  decomposition. 

We  can  obtain  some  idea  of  the  nature  of  the  products  of 
decomposition  from  the  methane  in  the  mines;  the  gases  in  the 
fresh  coal;  the  changes  of  fresh  coal  in  the  atmosphere  (which 
changes  are  a  continuation  of  the  process  of  carbonification), 
and  from  certain  laboratory  experiments  on  the  behaviour  of 
wood  in  an  atmosphere  of  oxygen. 

The  methane  in  the  coal  mines  is  a  real  product  of  decom- 
position. 

The  gases  held  in  absorption  by  coals  are  of  the  same  nature. 
Meyer  found  that  100  g.  of  coal  yield  from  17  to  59  cu.  cm.  of  a 
gas  containing  carbon  dioxide,  oxygen,  nitrogen,  methane,  ethane 
and  probably  butylene.  It  is  undecided  how  much  of  the  nitro- 
gen has  its  source  in  the  vegetable  matter  and  how  much  in  the 
atmosphere. 

155 


156  HEAT  ENERGY  AND  FUELS 

Relating  to  the  behavior  of  wood  in  an  atmosphere  of  oxygen, 
Saussure  observed  that  wood  shavings  enclosed  in  an  oxygen 
atmosphere  transformed  the  latter  into  the  same  volume  of 
carbon  dioxide.  The  same  observation  was  made  by  Liebig  for 
moist  and  old  wood.  Wiesner  found  that  the  first  stage  of 
decomposition  of  wood  consists  in  the  appearance  of  gray  color, 
whereby  the  intercellular  substance  vanishes  and  practically 
pure  cellulose  remains.  Moist  lignite  absorbs  oxygen  from  the 
atmosphere  and  generates  carbon  dioxide. 

Liebig  made  the  conclusion  from  his  experiments,  that  first  of 
all  the  hydrogen  of  the  wood  is  oxidized,  while  the  oxygen  of  the 
hydrate  water  combines  with  the  carbon  of  the  wood  to  form 
carbon  dioxide.  Considering  the  fact  that  methane  is  formed 
during  the  transformation  of  wood  into  coal,  he  calculates  that 
cannel  coal  can  be  explained  as  wood  fiber  less  3  molecules 
CH4,  3  mol.  H20  and  9  mol.  C02.  Brown  coal  is  oak  wood  less 
2  H20  and  3  C02,  etc. 

Relating  to  the  influence  of  the  exclusion  of  air  in  the  forma- 
tion of  coal,  Bischof  stated  that  atmospheric  oxygen  is  not 
essential  and  that  the  coal  deposits  must  have  been  formed 
mainly  under  exclusion  of  oxygen,  water  having  served  as  the  seal 
in  the  sea,  on  the  shores  and  in  meadows.  In  some  cases  the 
water  was  replaced  by  sand  and  clay  deposits.  The  ash  content  of 
coals  proves  this  fact.  The  oxygen  which  is  found  dissolved  in 
sea  water  certainly  did  not  have  much  effect,  since  according  to 
Hayes,  metals  kept  at  a  certain  depth  in  the  sea  are  not  oxidized. 

As  to  the  chemical  expression  of  the  carbonaceous  decom- 
position Balzer  says :  According  to  Bischof  there  are  three  ways 
possible  for  the  decomposition  to  take  place  according  as  carbon 
dioxide  and  water,  carbon  dioxide  and  methane,  or  carbon  diox- 
ide, water  and  methane  are  formed.  The  one  of  these  processes 
which  takes  place  is  determined  by  the  amount  of  the  react- 
ing air,  temperature  and  pressure.  When  vegetable  products 
during  the  carbonaceous  age  were  carried  by  rivers  into  basins 
of  salt  or  fresh  water,  where  formation  of  coal  took  place,  large 
quantities  of  methane  were  formed.  If  by  some  geological 
change  the  basin  becomes  dry,  the  process  goes  on  principally  as 
oxidation.  If  now  a  considerable  amount  of  sediment  is  deposited 
the  formation  of  coal  has  to  continue,  though  slowly,  without 
oxygen. 


FOSSIL  SOLID  FUELS 


157 


TABLE  LXIII. 

CHEMICAL  COMPOSITION  OF  FUELS. 

Uninflammable 
Coal. 

0 

OO                                                                            OO  O 
1  •*•                                                                           w  1    1 

0  0 

1    1 

WW                                                                    MWB 

«O  00                                                                                                                                             •<*  00    CC 

B  B 
S    1 

OO                                                                                        OO  O 

o  o 

BITUMINOUS  COALS. 

. 

i 

O                                                                          O  O 

1                                                 1   1 

^F|                                                                                   h"1  "n 

OO                                                                                                                                     00    OO 

o"                                                          o"  o" 

0                                                                                                                     "*<    0 

i 

I 

CQ 

o                                      oooo  o  :    • 

1                                                °»  I   1  °°   1    : 
o"                                                     O~O*"o~O~  o"  ; 

Jb  urther  by  absorbed  oxygen  
Remains  sand  coal  .  .  . 

T>,,  1  U..  

AJUIUCU  uy  UAygeri  

Remains  graphite  

BROWN  COALS. 

g 
g 

PQ  — 

xs  O 

I 

oooo  .  .  .  .  ;    ; 

W                                                                      i    CO  (M    rt<       •      •       •       •        . 

os                                       -1  •  ;  :  :    •       • 

g                               ^  *°  1  ®  :   :      :    :       :  a 

o"                            o"o~o~  o'  •  ;      •    :       •  | 
S3                              i  i  *"  8  :  :      :    :       :  * 

Bituminous 
Wood. 

o               0,0  o                 :  :      :    :      :| 
W                 WW  B~                               :       :  1 

-          ~  '  -                ;  i|  ;« 
s         ^s              ill  ;2 

H 

i 

ooo  o                5  :  :  :               :  -g  °    :B 

•«*<«O(M<M                                        ^-i-                  ^             "S'O-50 

•  "**  '    "*             ^    ':to:xSs^«so'T 

o^o^o"^  o~                  »     -2   '  ^   :  °  o  °  -g  .-^    :  l! 

cocoi«o                            .       t-i-2c^'73^2a>^'H<'c3 
co         Ico                             TS        Oo3a>Qo3c«>&iWiO 

WOOD. 

•      :      ct1'^  §o'      S  S>®  >  a  ^  ^»§S  a*3  °  9 

Sg  l|lf 

^S  S          g^ooS          'jco*'^"^    o       "5^'^    ^£3    ^fl 
Ocooi          c3^-^co        'S'^TJ'C    00"^^    On    So 
«o_i_i           i              ,         «<_       ^G^j^^flG^fcHa)^ 

158  HEAT  ENERGY  AND  FUELS 

According  to  Balzer  the  influence  of  temperature  is  as  follows : 
Low  temperature  decreases  the  velocity  of  coal  formation.  The 
temperature  in  the  deepest  part  of  the  Atlantic  Ocean  at  from 
49  to  57  degrees  latitude  is  2.1°  C.  In  regions  where  the  lowest 
winter  temperature  of  the  air  is  4°  C.,  the  deepest  layers  of  water 
have  a  constant  temperature  of  from  5  to  6°  C.  The  carbonifica- 
tion,  which  is  a  "voluntary"  decomposition  of  organic  subtances, 
is  certainly  an  exceedingly  slow  reaction  at  this  temperature,  and 
must  have  been  much  slower  yet  in  the  glacial  age. 

The  influence  of  pressure  is  as  follows :  It  is  uncertain  whether 
an  increase  in  pressure  increases  or  decreases  the  velocity  of 
car  bonification  and  the  optimum  of  pressure  is  also  unknown. 
We  cannot  make  any  deductions  from  the  fact  that  CaC03 
remains  undecomposed  at  high  pressure  since  in  organic  reactions 
with  closed  glass-tubes  the  generation  of  gas  and  chemical 
reaction  ordinarily  takes  place  at  high  pressure  and  high  tem- 
perature. Paraffin  is  decomposed  by  high  pressure  and  high 
temperature  in  hydrocarbons  of  the  methane  and  ethylene 
series.  In  such  cases  the  reactions  taking  place  change  with 
changes  in  temperature  and  pressure. 

A  certain  semi-soft  condition  of  the  wet  mass  can  be  con- 
sidered as  advantageous  for  the  reaction. 

Valuable  information  relating  to  the  changes  of  coals  in  the 
atmosphere  at  ordinary  and  higher  temperature  are  given  by 
Richter. 

It  is  known  that  coal  absorbs  oxygen  of  the  air.  Charcoal 
absorbs  nine  times  its  volume  of  oxygen.  Coals  absorb  gases 
as  readily  as  a  dry  sponge  absorbs  water.  If  coal  is  sat- 
urated with  one  gas,  some  other  gas  can  be  absorbed  in 
addition.  With  the  assistance  of  moisture  the  oxygen  is  com- 
pressed in  the  coal,  ozonised  and  thereby  becomes  chemically 
active,  causing  an  increase  of  temperature.  (Self-ignition  of 
powdered  coal.) 

Richter  observed  that  the  capacity  of  coal  for  absorbing 
oxygen  increases  up  to  200  degrees,  at  which  temperature  the 
absorption  stops.  Hydrogen  and  oxygen  are  absorbed  in  the 
proportion  2  :  16.  On  account  of  oxidation  in  the  air  deteriora- 
tion of  coal  takes  place,  shape  and  color  are  changed,  thermal 
value  and  coking  capacity  decreased. 

Since  only  a  part  of  the  hydrogen  of  the  coal  is  oxidized  the 


FOSSIL  SOLID  FUELS  159 

hydrogen  must  be  present  in  different  combinations,  which  is 
important  for  the  theory  of  the  constitution  of  coals. 

Considering  the  residuum  of  decomposition  Balzer  mentions 
the  constitution  of  the  wood-substance.  The  coals  are  chemical 
derivatives  of  cellulose,  consequently  of  the  wood-substance. 
The  constitution  of  these  substances  and  their  relations  to  each 
other  are  not  positively  known.  It  seems,  however,  that 
cellulose  does  not  occur  in  a  free  state  in  wood.  From  fir  wood 
we  can  isolate  by  extraction  with  ordinary  solvents  a  yellowish- 
white  substance  having  the  formula  C30H46021,  which  is  only 
slightly  soluble  in  ammoniacal  cupric  oxide,  being  thereby  essen- 
tially different  from  cellulose.  By  boiling  with  hydrochloric 
acid,  glucose  and  lignose  (C18H26On)  was  formed.  The  latter, 
which  is  also  insoluble  in  ammoniacal  cupric  oxide,  is  trans- 
formed by  boiling  with  nitric  acid,  into  cellulose  and  certain 
substances  of  the  aromatic  series.  From  these  reactions  we 
can  conclude  that  fir  wood  contains,  besides  the  cellulose-group, 
a  sugar-forming  and  an  aromatic  group,  so  that  its  composition 
is  much  more  complicated  than  that  of  cellulose. 

What  is  the  relation  of  wood  substance  to  coal?  It  is  known 
that  in  the  carbonaceous  decomposition  the  relative  quantity 
of  carbon  and  ash  increases  and  the  quantity  of  hydrogen, 
oxygen  and  nitrogen  decreases.  The  different  qualities  of  coal 
from  peat  to  anthracite  show  different  stages  of  this  process,  but 
the  formation  of  one  kind  of  coal  from  the  other  cannot  be 
expressed  by  a  chemical  equation. 

Balzer  makes  the  following  hypotheses  relative  to  the  con- 
stitution of  coals : 

1.  The  coals  are  mixtures  of  complicated  carbon  compounds 
(organic  substances), 

2.  Which  form  a  continuous  (or  possibly  homogeneous)  series. 

3.  The  carbon  ring  of  these  compounds  is  complicated  and 
somewhat  analogous  to  aromatic  compounds. 

Balzer  states  that  besides  the  carbonaceous  decomposition 
proper  a  destructive  distillation  can  take  place,  for  instance,  by 
contact  with  hot  bodies  or  fires.  In  Hessen,  Germany,  molten 
basalt  has  in  this  way  transformed  lignite  into  anthracite  coal, 
the  anthracite  deposit  changing  gradually  into  the  lignite  deposit. 
In  some  places  eruptive  porphyry  has  transformed  lignite  at  the 
contact  points  into  coke. 


160 


HEAT  ENERGY  AND  FUELS 


Supposing  an  increase  of  temperature  towards  the  center  of 
the  earth,  we  can  assume  100°  C.  at  a  depth  of  2600  m.  Products 
of  distillation  formed  in  these  regions  can  condense  in  the  upper 
regions,  the  lower  layers  forming  the  retort,  the  upper  the  con- 
densing chamber.  Balzer  believes  that  this  reaction  takes  place 
with  petroleum,  which  is  " distilled"  from  coal  deposits,  bitu- 
minous slates,  etc. 

Since  petroleum  occurs  in  silurian,  devonian  and  tertiary 
formations  it  is  apparent  that  the  place  of  " occurrence"  is 
different  from  the  place  of  "formation, "  which  can  be  explained 
by  distillation,  above  referred  to. 

Supposing  that  the  carbon  in  the  coals  is  present  as  such,  we 
consider  the  coal  deposits  as  end  products,  while  according  to 
the  above  mentioned  statement  they  are  in  a  process  of  contin- 
uous transformation,  which  hpwever  cannot  be  fully  explained  at 
present. 

The  fact  that  the  temperature  in  coal  mines  increases  with  the 
depth  faster  than  elsewhere  is  of  practical  importance  and 
theoretical  interest.  A  case  where  it  was  believed  that  hot 
springs  were  the  cause  of  the  high  temperature  of  the  mine  waters 
was  investigated  to  find  out  whether  the  formation  of  coal  is 
accompanied  by  a  sufficient  generation  of  heat  to  explain  the 
high  temperatures. 

The  following  results  were  obtained : 

TABLE  LXIV. 

AVERAGE    COMPOSITION    OF    FUELS.      (Muck.) 


Thermal 
Value, 
kg-cal. 

Wood 

50%  C 

6  %  H 

43     <y   o 

1  %  N 

—  4800 

Peat 

59%  C 

6  %  H 

33     %  O 

2  %  N 

—  6000 

Lignite  
Bituminous  coal  
Anthracite  

69%  C 
82%  C 
95%  C 

5.5%H2 
5  %H2 
2.5%H2 

25     %  02 
13     %  02 

2.5%  02 

0.8%  N2 
0.8%  N2 
Spur 

=  6800 
=  7900 
=  8300 

TABLE  LXV. 

THERMAL    VALUE    OF    THE    ELEMENTARY    CONSTITUENTS. 

Wood 0.50X8080+0.06  X 34, 000=  6080  kg-cal. 

Peat 0 . 59X  8080+  0 . 06  X  34,000=  6807  kg-cal. 

Lignite 0.69X8080+0.055X34,000=7445  kg-cal. 

Bituminous  coal 0.82X8080+0.05  X 34, 000=  8326  kg-cal. 

Anthracite 0 . 95X  8080+  0 . 025X  34,000=  8526  kg-cal. 


FOSSIL  SOLID  FUELS  161 

The  difference  between  the  thermal  value  of  the  elementary 
constituents  and  the  thermal  value  of  the  fuels  is  the  heat  of 
formation  of  the  respective  fuels  (see  Table  LXVI). 


TABLE  LXVI. 

FORMATION    HEAT    OF    FUELS. 


Wood                                           '• 

6080-4800=1280    kg-cal. 

Peat                                   

6807-6000=   807    kg-cal. 

Lignito                              

7445-6800=    645    kg-cal. 

Bituminous  coal 

8326—7900=   426   kg-cal 

Anthracit6 

8526—8300=    226    kg-cal 

The  heat  of  formation  decreases  with  the  increasing  thermal 
value. 

To  get  an  idea  about  the  quantity  of  fossil  fuel  produced  from 
wood  we  have  to  consider  the  gases  enclosed  in  the  coal,  as  these 
gases  are  also  produced  in  the  carbonizing  process.  They  are 
mainly  methane,  carbon  dioxide  and  nitrogen.  The  latter 
.proves  admission  of  air  to  the  coal  deposits.  Relative  to  the 
first  two  gases  we  find  carbon  dioxide  mainly  in  younger  coals 
(lignite)  and  methane  in  the  older  coals  (bituminous).  We 
therefore  have  in  the  younger  coals  mainly  a  formation  of  C02 
(heat  of  formation  8080  cal.  per  kg.  carbon),  in  the  older  coals 
mainly  of  CH4  (heat  of  formation  1833  cal.  per  kg.  carbon). 
Besides  this  the  formation  of  H20  (34,000  cal.  per  kg.  H2)  and 
of  small  quantities  of  heavy  hydrocarbons  (C2H4)  can  take 
place. 

Since  in  the  progressive  process  of  coal  formation,  the  heat 
of  formation  of  the  elements  decreases,  while  the  heat  of  forma- 
tion of  the  generated  products  of  decomposition  has  a  con- 
siderable positive  value,  the  heat  balance  of  the  coal  formation 
is  equal  to  the  difference  of  the  heats  of  formation  referred  to. 
The  balance  therefore  will  be  positive  if  the  heat  of  formation  of 
the  products  of  decomposition  is  greater  than  the  decrease  of 
the  heats  of  formation  of  the  fuels.  For  getting  this  effect  only 
a  very  small  amount  of  C02,  H20  or  CH4  is  required  as  is  shown 
in  Table  LXVIL 


162 


HEAT  ENERGY  AND  FUELS 


TABLE   LXVII. 
DATA  ON  THE  FORMATION  HEATS  OF  FUELS. 


Difference  between  the  Heat  of  Formation  of  Wood. 

This  Amount  of  Heat  Corresponds 
to  the  Heat  of  Formation  of 

C02        |       H20 

CH4 

and 

kg-cal. 

In  Per  cent  C  or  H2  of  the  original 
Weight  of  Wood. 

Peat. 

473 
635 

854 
1054 

5.8%C 
7.8%C 
10.  5%  C 
12.0%  C 

1.4%H2 
1.9%H2 
2-5%H2 
3.1%H2 

25.  7%  C 
34.6%  C 
46.  5%  C 

57.  4%  C 

Lignite 

Bituminous  coal  

Anthracite  

There  is  also  corresponding  to  the 


Difference  between  Heat  of  Formation  of 

C2O 

H20 

CH4 

From  Per  Cent 

Peat  and  lignite 

Per  cent 
l.OC 
2.7C 
1.5C 

Per  cent 
0.5  H2 
0.6H2 
0.6H2 

Per  cent 
8.9C 
11.  9C 
10.  9C 

Lignite  and  bituminous  coal  
Bituminous  coal  and  anthracite  

The  Formation  of 


If  these  figures  are  compared  with  the  difference  in  the  average 
composition  of  the  various  fuels,  we  see  that  the  formation  of 
coal  takes  place  accompanied  by  the  generation  of  heat. 

For  forming  an  approximate  idea  of  the  quantitative  changes 
during  the  transformation  of  wood  into  coal,  we  are  going  to 
deduct  the  changes  from  the  average  composition  of  the  different 
fuels,  following  Griesebach' s  (hypothetical)  table. 

We  therefore  have  for  the  formation  of  bituminous  wood : 


There  is  given  off: 

(a)  with  absorption  of  oxygen 
of  the  air  H2 

(/?)  directly  from  the  wood-sub- 
stance 3  CO,. 


C36H44022 


C3H2Oe 


=  wood. 


there  remains C33H42016       =  bituminous 

wood. 


FOSSIL  SOLID  FUELS  ,    163 

For  the  other  kinds  of  coal  we  can  imagine  the  process  of 
carbonification  as  follows : 

2  (C36H44022)  =  wood. 

There   is   given   off    from    wood 

2  (3  C02  +  2  H20) =  2(C3H408) 

there  remains 2  (C33H40014)   =  peat. 

From  peat  is  given  off : 


(a)  with  oxygen  of  the  air  4  HJ   ~  ^^  r\ 
(/?)  direct  6  H20  +  2  C02 J      L     10  5 


there  remains 2  (C32H3009)  =  earthy  lignite 

(brown  coal). 

From  earthy  lignite  is  given  off : 
(a)  by   reaction   with   oxygen 


2  (C4  +  H4) 
(/?)  direct  8  C02 


2  (C8H408) 


there  remains 2  (C24H260)    =  splint  coal. 

Therefrom  given  off  direct  4  C2H4     2  (C4H8) 

there  remains 2  (C20H180)    =  cannel  coal. 

From  this  is  given  off : 

(a)  by   reaction   with   oxygen 

9  H2 

(/?)  direct  H20 


there  remains C40H160          =  sand  coal. 

From  this  is  given  off : 

(a)  by   reaction   with   oxygen 


7 


08)  direct  H20 


H0 


16 


there  remains C40  =  graphite. 

This  enables  us  to  calculate  the  quantity  of  products  of  trans- 
formation obtained  from  wood  as  given  in  Table  LXVIII. 

From  Table  LXVIII  we  can  calculate  the  heat  of  formation 
of  the  different  fuels  as  given  in  Table  LXIX. 


164 


HEAT  ENERGY  AND  FUELS 


TABLE  LXVIII. 

PRODUCTS    OF    TRANSFORMATION    OBTAINED    FROM   WOOD. 


Fuel. 


Solid 

Substance 

kg. 


Gases  Generated  kg. 


C00 


H20 


Wood 1 

Peat 0.797         0.159      0.043 

Earthy  lignite 0.674         0.053      0.109 

Splint  coal 0.398         0.425      0.043 

Cannel  coal 0 . 333  0 . 067 

Sand  coal 0.309  0.109 

Graphite 0.290  0.086 

Bituminous  wood 0.838         0.159            0.022 

I.  Wood. 

Heat  of  formation  of  wood 1280  kg-cal. 

II.  Peat. 

Heat  of  formation  of  0.797  kg  peat 643  kg-cal. 

Heat  of  formation  of  0.159  kg  C02  =  347  call  ?  , 

Heat  of  formation  of  0.043  kg  H20  =  170  cal.j 
Heat  of  formation  of  wood  minus  heat  of  form. 

(peat  +  C02  +  H2O) m  120  kg-cal. 

The  transformation  takes  place  with  a  consumption  of  outside 
energy. 

III.   Lignite. 

Heat  of  formation  of  0.674  kg  lignite 435  kg-cal. 

Heat  of  formation  of  0.053  kg  C02  =  113  call          ™  ,        , 
Heat  of  formation  of  0.109  kg  H20  =  408  cal.J 
Heat  of  formation  of  peat  minus  heat  of  form. 

(lignite  +  CO2  +  H20) =313  kg-cal. 

The  formation  of  lignite  from  peat  takes  place,  accompanied 
by  the  generation  of  energy  (heat) . 

IV.   Bituminous  Coal. 

Heat  of  formation  of  0.346  kg  coal 147  kg-cal. 

Heat  of  formation  of  0.425  kg  C02    =  937  cal.     1 
Heat  of  formation  of  0.041  kg  C2H,  =  -  27  cal.  \ .  1206  kg-cal. 
Heat  of  formation  of  0.079  kg  H20  -  296  cal.    j 
Excess  of  heat  generation  over  the  difference  of  the 
heat  of  formation  of  lignite  and  coal  =  1206  - 
288 =918  kg-cal. 


FOSSIL  SOLID  FUELS  165 

Not  considering  bituminous  wood  wherein  we  find  similar 
conditions  as  in  peat,  we  have  the  following  excess  of  heat  in  the 
transformation  of: 

1  kg,  wood   in  0.797  kg  peat =  -      120  kg-cal. 

0.797  kg  peat     in  0.674  kg  lignite +    313  kg-cal. 

0.674  kg  lignite  in  0.346  kg  bit.  coal +    918  kg-cal. 

0.797  kg  peat     in  0.346  kg  bit.  coal +  1231  kg-cal. 

These  figures  are  not  absolutely  correct,  as  we  have  supposed 
only  the  formation  of  C02,  C2H4  and  H20,  while  according  to 
analysis,  especially  of  bituminous  coal,  CH4  plays  an  important 
part.  The  heat  of  formation  of  C2H4,  however,  is  —  642  cal.,  of 
CH4 1833  cal.  per  one  kilogram  of  carbon,  so  that  we  gain  +  2475 
cal.  for  every  kilogram  of  carbon  which  is  transformed  into  CH4 
instead  of  C2H4,  'while  we  lose  6247  cal.  for  every  kilogram  of 
carbon,  which  escapes  as  CH4  instead  of  C02.  Taking  even  this 
most  unfavorable  possibility  by  supposing  that  in  the  process 
of  carbonification  exclusively  CH4  and  H2  and  no  C02  at  all  is 
generated,  we  still  get  the  following  quantities  of  heat,  which 
are  produced  by  the  reaction 

1  kg  wood    in  0.797  kg  peat =  -  138  kg-cal. 

0.797  kg  peat     in  0.674  kg  lignite =  +  246  kg-cal. 

0.674  kg  lignite  in  0.346  kg  bit.  coal =  +  333  kg-cal. 

0.797  kg  peat     in  0.346  kg  bit.  coal =  +  579  kg-cal. 

Similar  results  were  obtained  by  F.  Toldt  and  F.  Fischer. 


CHAPTER  XL 
PEAT. 

PEAT  is  the  youngest  member  of  the  fossil  fuels,  and  the  result 
of  the  first  stage  of  carbonaceous  transformation  of  vegetable 
matter.  It  consists  mainly  of  decayed  moss  and  plants  growing 
in  bogs  and  swamps.  The  peat  deposits  can  be  classified  accord- 
ing to  Stentrupp  in  forest,  meadow  and  high  bogs.  While  the 
first  is  composed  of  decayed  trees  and  forest  plants,  the  two 
others  can  be  described  (Griesebach)  as  follows: 


Main  Components. 

Occurrence. 

Moss-peat  
Heath-peat  

Meadow-peat  

Sphagnum  varieties  
Roots  and  trunks  of  Erica  tetralix  . 
and  Calluna  vulgaris. 
Roots  and  trunks  of  Glumaccse  

In  all  bogs. 
In  high  bogs. 

In  meadow-bogs. 

F.  Schwackhoefer  proposes  the  following  classification: 

1.  High  bogs  (heath  and  moss  bogs)  are  found  in  higher  alti- 
tudes and  are  characterized  by  swamp-moss  (sphagnum),  heath- 
plants  (Calluna,  Erica,  Andromeda  and  Vaccinium),  also  by  the 
occurrence  of  mountain  pine  (Pinus  pumilis).     The  ground  is 
generally  clay  and  lays  above  the  level  of  summer  water.     The 
surface  is  always  curved.     In  some  localities  the  bog  is  10  to  15  m. 
thick. 

2.  Low  bogs   (meadow-bogs)  are  found  in  the  territory  of 
rivers,  creeks  and  lakes,  and  consist  of  plants  entirely  different 
from  the  high  bogs,  since  swamp  and  heath  plants  are  entirely 
absent.     Besides  some  Hypnum  varieties,  mainly  sour  grasses 
are  found  in  this  kind  of  peat.     The  ground  is  chalky  and  below 
the  level  of  summer  water.     The  layers  are  not  as  thick  as  in 
high  bogs. 

There  are  many  connecting  links   between  these  two  main 
groups.      Without  taking  into    consideration    the    origin   and 

166 


PEAT  167 

occurrence,  peat  can  be  classified  according  to  its  appearance 
(Karmarsch)  as  follows: 

A.  Turf -peat  (white  or  yellow). 

B.  Young  brown  and  black  peat. 

(a)  Fibrous  peat. 
(6)  Root-peat. 

(c)  Leaf-peat. 

(d)  Wood-peat. 

C.  Old  peat. 

(a)  Earth-peat. 

(6)  Pitch-peat. 

A.  Turf-peat.     Grayish  yellow  to  yellowish  brown  color  is  also 
called  white  or  yellow  peat.     Its  constituents  can  be  distinctly 
recognized  in  the  white,  spongy,  elastic,  fibrous  mass.     Enclo- 
sures of  roots  are  rare. 

B.  Young  brown  and  black  peat.     While  the  darker  color  shows 
a  further  progress  of  carbonaceous  decay,  the  organic  constituents 
can  yet  be  distinguished. 

(a)  Fibrous  peat  seems  to  be  formed  by  further  decomposi- 
tion of  turf-peat.     The  fibrous  structure  is  preserved,  but 
the  fiber  is  more  brittle  and  partly  earthy;  shows  less 
elasticity   and  is  densely  pressed  by  its  own  weight. 

(b)  Other  kinds  contain  short  fibers  only,  and  are  some- 
times earthy  to  a  large  extent. 

(a)  Thick,  light  brown,  tough,  long  fibers  (fibrous  peat). 
(/?)  Containing  roots  and  stems  (root-peat). 

(7)  Containing  dried  and  decayed  leaves  (leaf-peat). 
(d)  Containing  pieces  of  coarse  wood  (wood-peat). 

C.  Old  peat.    The  original  organic  structure  can  hardly  be 
distinguished.     On  account  of  the  progress  of  decomposition  the 
fibrous  texture  has  gone  over  into  earthy  structure,  occasionally 
of  such  density  that  the  peat  shows  a  sharp  and  brilliant  fracture. 
Organic  residue  such  as  roots  and  stems  are  rarely  found.     The 
color  is  brown  to  pitch  black.     The  strength  varies  considerably 
from  brittleness  to  extreme  hardness.     Accordingly  old  peat  is 
classified  into  the  following  varieties: 


168 


HEAT  ENERGY  AND  FUELS 


(a)  Earth-peat  (to  which  also  belong  drag-peat  and  swamp- 
peat)  with  earthy  texture,  rough  fracture  and  practically 
without  fibers. 

(6)  Pitch-peat,  dense,  heavy,  strong  and  with  smooth  frac- 
ture. The  average  composition  of  peat  is  given  in  Table 
LXIX. 

Ferstel  has  published  the  following  complete  analysis  of  a*  peat 
from  Upper  Austria : 

I.   Components  soluble  in  water . 
(a)  Organic  substances  with  traces 


of  ammonia 
(6)   Inorganic  substances 


CaS04 
NaCl 


Fe203 
A1203 
Li(X 


0.04  per  cent 
0.01  per  cent 
0.01  per  cent 
0.05  per  cent 
0.01  per  cent 
0.03  per  cent 


1.50  per  cent 


0.15  per  cent 


1.65  per  cent 


II.  Components  soluble  in  hydrochloric  acid, 
(a)  Organic  substances  with  traces 

of  ammonia  0.13  per  cent 

(6)  Inorganic  substances: 

P205 1.07  percent 

CaO 1.05  per  cent  3.07  per  cent 

MgO 0.30  per  cent 

Fe203 0.12  per  cent          2.94  per  cent 

MnO 0.04  per  cent 

A12O3 0.31  percent 

Li02 0.05  per  cent 

III.  Components  insoluble  in  water  and  hydrochloric  acid : 
(a)  Organic 

Ulmicacid 22.60% 


Ulmiccoal 34.70% 

Resin 4.10% 


Wax 


1.40% 


79.02% 


Vegetable  fiber .  . .  16.22% 

(6)  Inorganic 0.29% 

(c)  Water .14.05% 

Sum  98.08% 


93.36  per  cent 


PEAT 


169 


TABLE  LXIX. 
AVERAGE  COMPOSITION  OF  PEAT. 


Websky. 

Schwack- 
hoefer. 

Scheerer. 

Marsilly. 

Knapp. 

Composition  in  Per  cent. 

Air  Dry. 

Air  Dry. 

Free  of  Water  and  Ash. 

c  

49.6-63.9 
4.7-  6.8 
28.6-44.1 
0.0-  2.6 

50-60 
5-  6 
30-35 
1-  2 
10-20 
5-10 

45.0 
4.7 
25.3 

'25.6 

50-54 

7-  6 

|  43-40 

59.10 
5.83 

J35.16 

H  

O  

N 

H2O 

Ash 

The  ash-content  of  peat  varies  from  1.50  per  cent  and  has  the 
following  average  composition: 

Sand  and  clay  (mechanically  admixed) '. .'.    5.70% 

Silicic  acid  (from  plants  containing  silica) 1.30% 

Lime  (combined  partly  with  C02,  partly  with  H2S04)  10.50% 
Oxide  of  iron up  to  50% 

Only  traces  of  chlorine  and  alkalies  are  present.  The  content 
of  phosphoric  acid  sometimes  exceeds  6  per  cent,  which  has  to  be 
considered.  A  considerable  amount  of  sulphuric  acid  may  also 
be  present. 

The  specific  gravity  of  peat  varies  according  to  structure  and 
quantity  of  ash.  Karmarsch  found: 

Turf-peat 0. 113  to  0.263 

Young  brown  peat 0.240  to  0.676 

Earth-peat 0.410  to  0.902 

Pitch-peat 0.639  to  1.039 

By  dressing  (mechanically  purifying)  the  specific  gravity  can 
be  increased  to  1.3  to  1.4. 

Peat  is  easily  ignited  (easier,  the  looser  the  peat).  Very 
porous  varieties  show  a  point  of  ignition  of  200°  C. 

Peat  burns  with  a  long  smoky  flame. 


170  HEAT  ENERGY  AND  FUELS 

The  thermal  value  of  peat  is  as  follows  (in  calories) : 

Peat  with  30  per  cent  water  and  10  per  -cent  ash .   2090  Scheerer 

Peat  with  25  per  cent  water  and  free  of  ash 3800  Scheerer 

Peat  with  0   per  cent  water  and  15  per  cent  ash . .  4440  Scheerer 
Peat  with  0   per  cent  water  and  0  per  cent  ash .  . .   5250  Scheerer 

Dry  peat  free  of  ash • 5250  Tunner 

Dry  peat  with  4  per  cent  ash 5090  Tunner 

Dry  peat  with  12  per  cent  ash 4686  Tunner 

Dry  peat  with  30  per  cent  ash 3636  Tunner 

Peat  with  25  per  cent  water 3800  Tunner 

Peat  with  30  per  cent  water ; . . . .  3313  Tunner 

Peat  with  50  per  cent  water 2182  Tunner 

On  account  of  the  low  specific  gravity,  the  large  amount  of 
water  and  ash,  which  increases  the  cost  of  transportation,  also 
on  account  of  the  great  variety  in  quality,  peat  is  only  of  local 
importance  as  a  fuel. 

Lately  peat  has  been  used  as  a  disinfecting  material  and  for 
coarse  textile  products. 

Production  of  peat. 

1.  Cut  peat.     Peat  of  sufficient  consistency  is  cut  out  in  the 
shape  of  bricks.     For  the  purpose  of  digging  a  specially  shaped 
spade  is  used,  with  a  wing  at  one  side,  in  order  to  cut  out  rect- 
angular blocks. 

(a)  Peat  cut  by  hand. 

(a)  Horizontal  cut.    The  bricks  are  cut  out  horizontally. 
(ft)  Vertical  cut.     The  bricks  are  cut  out  vertically. 

(6)  Peat    cut    by    machine.    (Cutting    machine    systems, 
Brosowsky,  Diesbach  and  Hodge.) 

The  cut  peat  is  either  dried  in  piles  in  the  air  or  by  arti- 
ficial heat. 

2.  Molded  peat  (drag  peat).     Peat  which  is  too  earthy  (dry) 
or  too  swampy  (wet)  cannot  be  cut.     If  of  suitable  consistency 
it  is  molded  (formed)  directly,  otherwise  after  previous  moisten- 
ing (in  moistening  boxes)  or  desiccating  (in  tanks  or  on  dry 
earth).    The  molding  is  done  as  follows: 

(a)  The  wet  mass  of  peat  is  distributed  on  level  ground 
fenced  in  by  boards.     The  peat  is  given  proper  consistency 


PEAT 


171 


TABLE  LXX. 

ANALYSES  OF  PEATS. 


Origin. 

Composition  of  Dry  Peat. 

Mois- 
ture 
of  Air 
Dried 
Peat 

SpG 

Properties. 

Authority 

C 
Per 

Cent 

H 
Per 

Cent 

N 
Per 

Cent 

0 
Per 
Cent 

Ash 
Per 
Cent 

Cappoge,  Ireland  .  . 
Kulbeggen,  Ireland 

Philipstown,    Ire- 
land. 
Wood  of  Allen,  Ire- 
land. 

Vulcaire,  near  Ab- 
beville. 

Lony,  near  Abbe- 
ville. 
Framont    . 

51.05 
61.04 
58.69 

61.02 
57.03 
58.09 
57.79 
62.15 
57.50 
47.90 

50.13 

to 
55.01 

57.16 
59.86 
50.85 
57.84 

57.03 
53.59 

45.44 

46.75 
to 
60.79 

56.43 
53.51 
57.20 

49.88 
50.86 
62.54 
59.47 
59.70 

58.93 
59.61 
54.01 

46.78 
58.51 
40.10 
51.38 

6.85 
6.87 
6.97 

5.77 
5.63 
5.93 
6.11 
6.29 
6.90 
5.8 

4.20 
to 
5.36 

5.65 
5.52 
4.64 
5.85 

5.56 
5.60 

5.28 

3.57 
to 
7.01 

5.32 
5.90 
5.32 

6.5 
5.80 
6.81 
6.52 
5.70 

5.72 
5.43 
4.84 

4.38 
6.17 
4.53 
6.49 

^9 
3^ 
1.4T 

0.81 
2.09 

s^^». 

31 

N»^. 

30 
1.66 
1.75 
42" 

*^^. 

31 

t 
35 

—  - 

33 

>i^». 

33 

^-*-. 

30 
0.95^ 

1.67 
2.71 

1.46 

0.67 
to 
6.33 

^-*-s 

38 

>^», 

40 

>^^, 

37 

1.16 
0.77 
1.41 
2.51 
1.56 

>•*•», 

35 

^M^S 

31 

>—••-», 

28 

N—  , 

28 

7? 

2.84~ 
1.68 

^5 

***** 

46 
"32.88 

32.40 
29.67 

i*^' 

77 

"^' 

37 
27.20 
31.81 
^0 

~I4 
» 

24 

-*-' 

39 

,*^,' 

71 

/-•—•' 

25 

•*—»-'. 

32.76 

34.15 
30.32 

26.21 

26.87 
to 
f  49.01 

i^W 

35 

,^*S 

59 

.—  »—  ' 

56 

42.42 
42.70 
29.24 
31.51 
33.04 

,^^" 

35 

/^*-s 

64 
^56 

,—i_- 

56 
7J 
^21.51 
35.43 

2.55 
1.83 
1.99 

7.90 
5.58 
4.61 
3.33 
2.70 
2.04 
3.50 

8.20 
to 
21.17 

3.80 
0.91 
14.25 
2.6 

1.57 
8.10 

21.60 

0.89 
to 
14.76 

9.86 
6.60 
2.31 

3.72 
0.57 
1  09 
18.53 
2.92 

8.43 
3.32 
12.59 

20.28 
4.21 
7.87 
5.02 

t 

_o 

0 

16.7 
16.0 
17.0 

15.17 
to 
21.7 

0.405 

0.619 
to 
0.072 

Pale,    red- 
brown. 

Dark   brown, 
dense. 

Dark  brown. 
Same. 

Incompletely 
decomposed. 
Solid  and 
dense. 
Somewhat 
lighter. 
Light,    felty 
mass. 

Dense  

Kane 
....Do. 

....Do. 

.  .  .  .Do. 
Re"gnault 
.  .  .  .Do. 
.  .  .  .Do. 
Walz. 
.  .  .  .Do. 
....Do. 

Mulder 
.  .  .  .Do. 
.  .  .  .Do. 
Braunin- 

...gfiro. 
....Do. 

....Do. 

(  Nessler 
and 
(  Petersen 

Jaeckel. 
....Do. 
...Do 

Websky. 
.  .  .Do. 
...Do. 
...Do. 
Do 

Rammstein, 
Rheinfalls. 
Steinwenden, 
Rheinfalls. 
Niedermoor, 
Rheinfalls. 

Prussia     .   .       .     . 

Friesland  

Light 

Holland 

Bremen  

Bremen  
Schopfloch,    Wurt- 
temberg. 
Sindelfingen, 
Wiirttemberg. 

Baden 

20.6 
18.0 

11.77 
to 
18.55 

17.63 
19.32 
18.83 

* 
* 
* 

Dark   brown, 
dense,  heavy 
Same  
Dark  brown, 
dense. 
Same  

Heavy,  dense, 
brown. 
Light,  loose. 

Red   brown, 
heavy 

Berlin,    Havelnie- 
der. 
Berlin,    Havelnie- 
der. 
Hamburg,  Moor  .  .  . 

Grunewald  
Harz  . 

Harz  

Limm  
Hundsmiihl  

Haspelmoor  
Neustadter  Hiitte. 
Montanger.  

15.50 
10.31 
17.11 

15.72 
15.50 
23.17 

p 
1.07 

Pressed-peat. 
Do  

Peat  prepared 
after  Challe- 
ton. 
Same   . 

Kraut. 
...Do. 

...Do. 
Do. 

Neufchatel  
Kolbermoor  
Switzerland  
Schonen  

Pressed-peat  . 
Same  

Wagner. 

Goppels- 
roder. 
Jacobsen. 

Very  dense  .  .  . 

*  Calculated  free  of  ash. 


172  HEAT  ENERGY  AND  FUELS 

by  evaporation,  trickling  of  the  water  into  the  ground, 
by  pounding,  treading  and  beating.  The  boards  are  then 
removed  and  the  mass  cut  with  sharp  knives  into  regular 
bricks. 

(6)  The  mass,  compressed  from  the  top  is  beaten  into  forms, 
(a)  Containing  only  one  brick  (beaten  peat). 
(/?)  Containing  space  for  several  bricks  (molded  peat). 

3.   Machine  peat. 

(a)  Without  pressure  (machine  peat  proper).    The  cut  peat 
is  formed  into  bricks  and  dried.     Occasionally  it  is  pre- 
viously carded  so  as  to  get  a  denser  product. 

(b)  With  pressure   (pressed  peat). 

(a)  Dry  pressed :  small-sized  peat  is  sifted,  dried  by  heat, 
and  briquetted  in  a  heavy  brick  press.  Such  peat  is 
expensive  on  account  of  the  cost  of  drying  and  is  dis- 
integrated by  heat. 

(/?)  Wet  pressed,  most  of  the  water  is  removed  by  pressure. 
There  are  many  constructions  of  peat-brick  presses  in 
successful  use. 

Peat  molded  in  the  form  of  balls  or  eggs  is  very  convenient  to 
handle  and  makes  firing  easy.  Analyses  of  some  dry  peats  are 
given  on  page  171. 


CHAPTER   XII. 
BROWN-COAL   (LIGNITE). 

BROWN-COAL  is  the  next  stage  of  carbonaceous  decay  and  was 
formed  mostly  by  transformation  of  plants  rich  in  resin  (conifer- 
ous trees,  palm  tree  and  cypress;  later,  also  leaved  trees). 

The  specific  gravity  of  this  coal  varies  from  0.8  to  1.8  (in  coals 
very  high  in  ash),  but  in  most  cases  from  1.2  to  1.5.  It  has 
various  colors,  and  the  touch  is  generally  brown.  In  the  air 
brown-coal  easily  absorbs  oxygen  and  evolves  carbon  dioxide, 
whereby  on  account  of  the  loss  in  carbon,  the  thermal  value  is 
decreased ;  at  the  same  time  the  temperature  is  increased  and  in 
large  piles  causes  spontaneous  combustion. 

Brown  coal  does  not  occur  before  the  tertiary  period.  The 
gases  found  in  brown-coal  deposits  consist  generally  of  carbon 
dioxide  (not  of  hydrocarbons  as  in  soft-coal  deposits).  Zitowich 
published  the  gas  analyses  of  such  coals  (Table  LXXI). 

TABLE  LXXI. 

ANALYSES    OF    GASES    FOUND    IN    BROWN-COAL.      (Zitowich). 


In  Bohemian  Patent-Brown  Coal. 

In  Earthy  Coal 
of  Inferior  Quality. 

CO2 

89.66 
1.80 
8.03 
0.51 

82.40 
3.00 
14.15 
0.45 

83.99 
1.04 
14.91 
0.65 

CO 

N                            .... 

0  

Sum  

100.00 

100.00 

100.59 

Gases  from  : 

Julius-Mine  in  Bruex  (Bo- 
hemia) . 

Coal  from 
Rossitz. 

Coal  from 
Habichtswald. 

CO, 

37.62 

35.13 

31 

91 
9 

CO 

CEL 

33.34 
29.04 

36.06 

28.81 

30 
20 

19 

N 

O.. 

C.,Hf  . 



173 


174  HEAT  ENERGY  AND  FUELS 

While  previously  the  brown-coals  were  classified  as  lignite  or 
fibrous  brown-coal,  earthy  brown-coal  and  conchoidal  brown- 
coal,  Zinken  has  suggested  the  following  classification : 

1.  Common  brown-coal.     Compact,  more  or  less  dense  and 
strong.    The  fracture  may  vary  in  character  from  dense  to 
earthy;  in  structure  it  may  be  more  or  less  conchoidal;  in  appear- 
ance it  may  vary  from  dead  to  slightly  brilliant;  in  color  from 
light  brown  to  dark  brown,  and  light-brilliant  touch.    This  coal 
is  between  earth  coal  and  pitch-coal,  and  is  produced  in  all  sizes. 

2.  Earthy  brown-coal.     More  or  less    brittle,  light    to    dark 
brown,  showing  dead,   uneven   fracture,   without  any  organic 
structure.     The  lighter  varieties  burn  with  a  long,  the  dark  ones 
with  a  short,  but  intense  flame. 

3.  Lignite  or  fibrous  brown-coal.     More  or  less  fossil  wood- 
substance,  yellow  to  dark  brown,  specific  gravity  0.5  to  1.4, 
fracture  depending  on  the  nature  of  the  wood. 

4.  Slate-coal.    Slaty,  dense,  dark-brown  to  black. 

5.  Paper-coal.  Thin,  elastic  layers  of  gray  to  dark-brown  color. 

6.  Leaf-coal.    Formed  of  very  thin  leaves  of  plants. 

7.  Reed-coal.    Reed-like  strips  formed  into  ribbon-like  layers. 

8.  Moor-coal.    Compact    without    wood-texture,    of    even, 
uneven  or  conchoidal  fracture,  sometimes  slaty,  mostly  loose, 
spongy  and  brittle ;  dark  brown  to  pitch  black.     Specific  gravity 
1.2  to  1.3.     Occurs  mostly  in  the  lower  part  of  lignite  deposits. 

9.  Pitch-coal.    Compact,  brittle  to  tough,  mostly  weak,  black- 
brown  to  pitch  black;  has  the  lustre  of  pitch  or  wax.     Brown 
touch;  fracture  imperfect  to  conchoidal.     Specific  gravity  1.2  to 
1.3.     Occurs  near  volcanic  rocks. 

10.  Lustre-coal.    Compact,  conchoidal,  jet  black,  very  brilliant. 
The  hardest  and  strongest  variety.     Specific  gravity  1.2  to  1.5. 

11.  Gagat  (from  the  river  Gages  in  Licia).     Dense,  conchoidal, 
pitch-black.     So  strong  that  it  can  be  worked  into  ornaments. 

12.  Stalky  brown-coal.     Like  common  brown  coal  but  stronger. 
The  average  composition  of  brown  coals  is : 

Carbon 50  to  65  per  cent 

Disposable  Hydrogen 1  to    2  per  cent 

Water  chemically  combined 20  to  30  per  cent 

Water  hygroscopic 10  to  25  per  cent 

Ash 5  to  10  per  cent 


BROWN-COAL 


175 


The  quantity  of  nitrogen  present  is  nearly  always  less  than  1 
per  cent.  The  quantity  of  water  varies  as  follows : 

Fresh-mined  coal 30  to  40  per  cent 

Sometimes  up  to 60  per  cent 

In  air-dry  coal 10  to  30  per  cent 

Coal  which  has  been  completely  dried  at  100  degrees  absorbs 
in  the  air  from  10  to  15  per  cent  of  moisture.  The  ash  varies  from 
1  per  cent  to  over  50  per  cent ;  it  may  contain  from  1  to  2  per  cent, 
and  sometimes  more,  sulphur  combined  with  iron  (detrimental 
sulphur). 

The  organic  components  in  brown-coal  are  mainly  ulmic  acid, 
its  derivatives  and  resinous  substances.  Otherwise  the  compo- 
sition varies  considerably  even  in  coals  from  the  same  mine. 

The  following  table  shows  the  composition  of  some  brown- 
coals  : 

TABLE   LXXII. 

COMPOSITION    OF    BROWN-COALS. 


Gas. 

Coke. 

Composition  of  Coal  in  Per  cent. 

§ 

Sulphur. 

S-j 

—  .      «8 

Place. 

§  v 

Yield: 

s  &° 

Per  cent. 

C 

H 

0 

N 

H2O 

Ash. 

I* 

•°  jo 

1  * 

H 

• 

i 

H 

° 

I.  Austria  Hun- 

gary: 

(1)  Styria: 

Johnsdorf.  .  . 

25.73 

63.32 

6.03 

4.92 

0.96 

Leoben  

30.07 

54.82 

10.77 

4.34 

Trifail  

49.95 

3.67 

16.'93 

0~97 

20.15 

8.43 

1.64 

4386 

(2)  Bohemia: 

Teplitz  

44.93 

3.21 

12.51 

0.64 

34.28 

4.43 

0.50 

3925 

Dax 

50.12 

4.06 

13.14 

0.65 

25.50 

6.53 

0.93 

4630 

II.  Germany. 

Elbogen  

26.0 

77.64 

7.85 

14.51 

Cologne  

63.42 

4.98 

27.11 

III.  France. 

Dax  

46.6 

74.19 

5.88 

20.13 

Middle  Alyses 

48.0 

72.19 

5.36 

22.45 

IV.  Ireland: 

Lough  Neagh  . 

58.56 

5.95 

26.85 

As  can  be  seen  from  the  above  table  the  composition  of  brown- 
coal  of  the  same  origin  and  mine  varies  considerably.     It  is, 


176 


HEAT  ENERGY  AND  FUELS 


therefore,  very  difficult  to  get  an  exact  average  sample  for  analy- 
sis. For  determining  the  non-uniformity  in  the  composition, 
the  author  broke  several  small  pieces  from  a  piece  of  coal  (of 
Johnsdorf)  about  the  size  of  a  fist.  The  results  of  the  analysis 
are  given  in  Table  LXXIII. 

TABLE   LXXIII. 

COMPOSITION    OF    BROWN-COALS. 


No.  of  Test. 

Percentage  of 
Hygroscopic 
Moisture. 

Yield  in  Gas. 
Percentage. 

Percentage  of 
Coal  Resid- 
uum. 

Percentage  of 
Ash. 

1 

8.49 

28.57 

53.85 

9.09 

2 

8.02 

29.07 

53.57 

9.34 

3 

7.77 

27.95 

54.79 

9.49 

4 

7.63 

28.41 

54.15 

9.81 

5 

6.87 

31.67 

52.31 

9.15 

6 

9.13 

'      29.76 

53.27 

9.94 

7 

8.17 

28.81 

53.21 

9.81 

8 

7.24 

31.90 

51.54 

9.32 

Average.  . 

7.91 

29.52 

53.33 

9.37 

Another  series  of   tests  with  the  same  piece  are  given  in 

Table  LXXIV. 

TABLE  LXXIV. 

COMPOSITION    OF    BROWN-COALS. 


Weight  of  the  Lead  Regulus 

Oxygen  in  kg. 

in  Grams. 

Theoretically 

No.  of  Test. 

Grams  Used. 

Required  for 

Directly 
Found. 

Per  1  g.  Fuel. 

Burning  1  kg. 
of  Fuel. 

1 

1.00 

21.98 

21.98 

1  .  6990 

2 

1.00 

22.31 

22.31 

1  .  7245 

3 

5.00 

110.30 

22.06 

1.7052 

4 

5.00 

109.38 

21.88 

.6910 

5 

5.00 

111.59 

22.795 

.7252 

6 

5.00 

111.36 

22.68 

.7216 

7 

5.00 

111.68 

22.34 

.7269 

8 

5.00 

115.42 

23.08 

.7841 

9 

5.00 

110.09 

22.02 

.7021 

10 

5.00 

112.52 

22.50 

.7393 

Average  .  . 

22.3645 

1.72189 

BROWN-COAL 
Table  LXXV  gives  several  analyses  of  brown-coal  ash. 

TABLE   LXXV. 
COMPOSITION    OF    BROWN-COAL    ASH. 


177 


Coal  Ash  from  .... 

Artern. 

Helmstedt. 

Gross- 
Priessen. 

>5 

d 

*•<!> 

1 

w 

Lignite  from 
Meissner. 

Seegraben  b. 
Leoben. 

Fohnsdorf. 

tic 

3 

1? 

r 

Analyst  

Krem- 
ers. 

Var- 
ren- 
trapp. 

O.  Kot- 

tig. 

Son- 
nen- 
schein. 

Jliptner 

SiO2  .  . 

3.12 
9.17 

17.27 
33.83 

20.67 
15.45 

13.52 
1.23 

36.01 
12.35 

23.7 
5.05 
1.13 

15^62 
3.64 
2.38 
0.38 
1.55 

20.5 
30.3 

14^7 
18.1 

io!o 

3.4 
1.9 

2.88 

0^23 
Trace 
14.62 
39.28 

13.47 

6!l3 

17.47 
5.32 
15.96 

2.52 

0^15 
10.86 
12.17 
45.44 

so,  

P2O.  

Cba... 

A12O  

29.50 
32.18 

11.57 
5.57 

Fe9O,.. 

MnO  

Mn.O4   .  . 

7.43 
34.15 
0.94 

|o.47 

19.86 
15.67 
0.38 

jll-71 

2.35 
16.60 
Trace 

J9.91 

CaO 

20.56 
2.16 
0.99 
1.72 

23.67 
2.58 
1.90 

45.60 

T67 

1.86 

MgO 

K2O  

Na,O 

Chlorine 

Total  

99.40 

96.39 

100.00 

101.81 

98.9 

100.00 

100.00 

100.00 

CHAPTER  XIII. 
BITUMINOUS    AND    ANTHRACITE    COALS. 

A.   BITUMINOUS  COAL. 

THE  older  fossil  coals,  ordinarily  called  bituminous  coals,  are 
mostly  black  in  color  and  have  a  high  lustre;  no  organic  structure 
can  be  discerned  without  a  microscope.  The  fracture  varies. 
The  coals  are  not  hard  but  brittle. 

In  destructive  distillation  they  yield  more  solid  residuum  and 
less  water  than  the  fuels  previously  treated  and  their  tempera- 
ture of  ignition  is  higher. 

The  great  commercial  importance  of  bituminous  coals  early 
caused  their  division  into  groups,  many  different  schemes  being 
proposed. 

Schondorf  based  his  classification  on  the  coking  quality: 

Coke  rough,    f  loose I.  Sand-coal. 

fine,  sandy  <  molten  hard,  loose  in  the  center. .  II.  Molten  sand-coal 

and  black.    '  molten  hard  all  over III.  Sinter  coal. 

Coke  gray  and  solid,  opening  like  a  bud III.  Baked-sinter-coal. 

Coke  smooth,  metallic,  strong V.  Baking  coal. 

Gruner  based  the  following  classification  on  the  character  of  the 
flame: 

I.  Long-flame  sand-coals  (sand-coal  rich  in  gas)  can  be  used 
for  reverbatory  furnaces  and  as  inferior  gas  coal.  They  burn 
with  long,  smoky  flame,  crack  in  the  heat,  and  disintegrate 
without  baking. 

Sand  coal.  — Composition  of  coal  substance: 

C  =  75     to  80     per  cent 


J. 

H  =     5.5  to    4.5  per  cent 
0  +  N  =   19.5  to  15.5  per  cent 


The  ratio  of  (0  +  N)  to  H  equals  3  or  4. 
By  destructive  distillation  these  coals  yield  from  50  to  60  per 
cent  of  sandy  to  slightly  molten  coke,  evaporate  from  6.7  to  7.5 

178 


BITUMINOUS  AND  ANTHRACITE  COALS  179 

times  their  weight  of  water  and  have  a  thermal  value  of  8000  to 
8500  cal. 

The  soot-coal,  which  is  of  fibrous  structure  and  contains  only 
3  per  cent  of  hydrogen  also  belongs  to  this  class. 

II.  Long-flame  baking  coals  (long-flame  caking  coals,  gas-coals, 
sinter  and  baking  coals  rich  in  gas)  are  used  mainly  as  flaming 
coals  and  gas-coals,  less  suitable  for  coking  (however,  in  special 
ovens  a  coke  of  medium  quality  can  be  produced).  They  burn 
with  a  long,  smoky  flame,  get  soft  in  the  heat  and  fritted.  (Coals 
standing  in  quality  between  these  coals  and  the  long-flame  sand- 
coals  are  called  sinter-coals). 

Composition  of  coal  substance: 


C  =  80    to  85  per  cent 

H  =    5.8  to    5  per  cent 

O  +  N  =  14.2  to  10  per  cent 


The  ratio  of  (0  +  N)  to  H  equals  2  or  3. 

Coke  residuum  of  destructive  distillation  60  to  68  per  cent  (per- 
fectly molten,  not  baked).  These  coals  evaporate  7.6  to  8.3 
times  their  weight  of  water  and  generate  8500  to  8800  cal. 

III.  Baking  coals  proper  (medium-flame  caking  coal,  forge 
coal),  especially  adapted  to  coking,  gas  making  and  heating. 
Burn  with  less  smoke  and  more  brilliant  flame  than  the  previous 
kinds,  melt  in  the  heat  and  bake  together  to  solid  masses. 

Composition  of  coal  substances : 


C  =  84  to  89  per  cent 

H  =      5  to  5.5  per  cent 

0  +  N  =  11  to  5.5  per  cent 

O  +  N 


H 


=  I  or  2. 


Coke  residuum  by  destructive  distillation  from  68  to  74  per 
cent;  the  coke  is  molten  and  more  or  less  puffed.  These  coals 
evaporate  from  8.4  to  9.2  times  their  weight  of  water  and  generate 
from  8800  to  9300  cal. 

IV.  Short-flame  baking  or  caking  coals  (coking  coal  poor  on 
gas).  Best  coking  and  boiler  coal.  Difficult  to  ignite,  burns 
with  an  illuminating,  short,  slightly  smoky  flame.  Cakes  some- 
what in  the  heat. 


180  HEAT  ENERGY  AND  FUELS 

Composition  of  coal  substance: 

C  -  88    to  91     per  cent 

H  =    5.5  to    4.5  per  cent 

0  +  N  =    6.5  to    4.5  per  cent 

0  +  N 

— == —  =  about  1. 
H 

Coke-residuum  of  destructive  distillation  from  74  to  82  per  cent. 
The  coke  is  molten,  and  compact.  These  coals  evaporate  from 
9.2  to  10  times  their  weight  of  water,  and  generate  from  9300  to 
9600  cal. 

V.  Anthracitic  coals  (poor  in  gas,  older  sand-coals) .  Especially 
adapted  to  shaft  furnaces,  boilers  and  domestic  uses.  Cannot  be 
coked.  Difficult  to  ignite ;  burn  with  short,  weak  and  practically 
non-smoking  flame.  Cakes  slightly  in  the  heat  and  frequently 
disintegrates. 

Composition  of  coal-substance : 

€  =  90    to  93  per  cent 

H  =    4.5  to    4  per  cent 

0  +  N  =    5.5  to    3  per  cent 

0  +  N 


H 


=  about  1. 


Residuum  of  destructive  distillation  from  82  to  90  per  cent, 
slightly  molten,  mostly  sandy.  These  coals  evaporate  from  9  to 
9.5  times  their  weight  of  water  and  yield  from  9200  to  9500  cal. 

A  similar  classification  was  made  by  Hilt.  If  we  determine 
the  ratio  (in  weight)  of  volatile  matter  to  the  coke  dried 
at  100  degrees  and  free  of  ash,  we  get  the  results  shown  in 
Table  LXXVI. 

TABLE  LXXVI. 

CLASSIFICATION    OF    COAL.      (Hilt.) 


Kind  of  Coal. 


T 

Anthracite                                    .  .                  

1  :  20 

to 

1  •  9 

II. 
III. 
TV 

Semi-caking  sinter-coal  (poor  in  gas)    
Caking  or  baking  coal  
Baking  gas-coal                             

1  :  9 
1  :  5.5 

1  :  2 

to 
to 
to 

1  :5.5 
1  :2 
1:15 

V 

Sinter-coal  rich  in  gas  

1  :  1.5 

to 

1  :  1.25 

VT 

Sand-coal  rich  in  gas                                           .    .  • 

1  •  1  25 

to 

1  •  1   11 

Ratio  of  Residuum, 
Free  of  Ash  and  Vol- 
atile Matter. 


BITUMINOUS  AND  ANTHRACITE  COALS  181 

Expressing  the  volatile  matter  as  given  in  Table  LXXVI  in 
per  cents  free  of  ash,  we  get  the  results  given  in  Table  LXXVII. 


TABLE   LXXVII. 

CLASSIFICATION    OF    COAL.      (Hilt.) 


Kind  of  Coal. 

Volatile  Matter. 
Per  cent. 

T 

Anthracite                  \  

5       to   10 

II 

Semi  caking  coal 

10       to  15  5 

III 

Caking  coal 

15  5  to  33  3 

IV 

Baking  gas-coal 

33  3  to  40 

v 

Sinter-coal  rich  in  gas                         

40       to  44  4 

VI. 

Sand  -coal  rich  in  gas  

44.4  to  48 

Dr.  E.  Muck  based  a  classification  on  simple  laboratory  experi- 
ments. 

If  a  small  quantity  (about  a  teaspoonful)  of  finely  powdered 
coal  is  quickly  heated,  preferably  in  a  platinum  crucible,  until  no 
flame  is  visible  at  the  cover,  the  quality  of  the  cooled  residuum 
varies  according  to  the  coal  used,  as  follows: 

Powder,  just  like  the  coal-powder  used .  .      I.  Sand-coal. 

Somewhat  molten,  partly  powder II.  Molten  sand-coal. 

Molten  but  not  puffed. III.  Sinter-coal. 

Molten,  somewhat  puffed IV.  Caking  sinter-coal. 

Thoroughly  molten  and  puffed  up  in  a 

form  similar  to  a  potato V.  Caking  coal. 

The  properties  are  the  same  in  using  the  fuel  on  a  large  scale. 
In  heating  under  admission  of  air  (grate-firing),  I,  II,  and  III  do 
not  melt;  but  IV  and  V  do  melt  to  such  an  extent  as  to  clog  the 
grate  openings,  so  that  only  I,  II  and  III  can  be  used  under  boilers 
and  for  household  purposes. 

If  melting  (caking)  coals  III  and  IV  are  slowly  and  gradually 
heated,  they  do  not  melt  properly  and  the  coke-residuum  is  poor- 
looking,  soot-black  and  strongly  puffed.  This  also  takes  place  at 
high  temperature  and  too  large  an  air  supply,  since  the  fusible 
coal  substance  is  destroyed  by  long  heating  (partial  degasifica- 
tion)  and  excess  of  air  (oxidation).  If  caking  coal  is  heated  for 


182 


HEAT  ENERGY  AND  FUELS 


some  time  in  the  open  air  (to  about  300  degrees),  it  no  longer 
cakes  at  all  if  afterwards  heated  to  a  high  temperature. 

Depending  on  the  fact,  whether  the  coal  sample  is  heated  to 
high  (normal  test)  or  low  temperature  (puffing  test)  the  coke 
obtained  shows  different  volume  and  color.  After  heating  to  a 
high  temperature  the  volume  is  smaller  than  after  heating  to  a 
low  temperature.  The  color  after  the  normal  test  is  more  or 
less  brilliant,  silver- white,  after  the  puffing  test  black  and  not 
brilliant.  We  find  the  same  phenomena  in  coke  ovens  at  low 
and  high  temperature. 

Considering  besides  the  quality  of  the  coke,  the  fusibility  and 
the  flame  of  the  coal,  the  classification  given  in  Table  LXXVIII 
can  be  used  (Muck). 

TABLE   LXXVIII. 

CLASSIFICATION    OF    COALS. 


Elementary  Compo- 

Yield 

sition  of  the  Coal, 

Quality. 

Dry  and  Free  of  Ash, 
in  Per  cent. 

in 
Coke, 
Per 

Quality  of  Coke. 

Specific 
Gravity. 

cent. 

c 

H 

O 

I.    Dry  bituminous 

75 

5.5 

19.5 

50 

Powdered      or 

1.25 

coal     with     long 

to 

to 

to 

to 

fritted. 

flame. 

80 

4.5 

15.0 

60 

II.   Baking   bitum. 

80 

5.8 

14.2 

60 

Molten  and  ri- 

1.28 

coal     with     long 

to 

to 

to 

to 

mous. 

to 

flame,  or  gas  coal. 

85 

5.0 

10.0 

68 

1.3 

III.   Baking       coal 

84 

5.0 

11.  .0 

68 

Molten      and 

1.3 

proper,    or    forge 

to 

to 

to 

to 

compact. 

coal. 

89 

5.5 

5.5 

74 

IV.   Baking      bitu- 

88 

5.5 

6.5 

74 

Molten,     very 

1.3 

minous  coal  with 

to 

to 

to 

to 

compact, 

to 

short     flame,     or 

91 

4.5 

5.5 

82 

slightly     ri- 

1.35 

coke-coal. 

mous. 

V.  Semi-anthracitic 

90 

4.5 

5.5 

82 

Fritted  or  pow- 

1.35 

coal. 

to 

to 

to 

to 

dered. 

to 

93 

4.0 

3.0 

90 

1.4 

From  these  figures  we  see  the  relation  and  connection  between 
the  properties  of  the  coals  and  their  chemical  compositions.  But 
there  are  also  cases  of  isomerism  where  coals  of  about  identical 
composition  show  an  entirely  different  behavior  in  heat. 


BITUMINOUS  AND  ANTHRACITE  COALS 


183 


TABLE   LXXIX. 
CLASSIFICATION    OF    COALS. 


Occurrence. 

Composition  of  Coal, 
Dry  and  Free  of  Ash, 
in  Per  cent. 

Yield 
of 
Coke, 
Per 
cent. 

Quality  of  Coke. 

C 

H 

O-f-N 

Niederwuschnitz,  Saxony  .  . 
Zwickau   Saxony  

82.34 

82.59 
87.47 

'87.79 

4.73 
4.76 
5.03 

4.78 

12.93 
12.65 
7.50 

7.24 

66.43 
77.29 
75.80 

77.60 

Sandy. 
Caked. 
Slightly  molten. 

Caked  and 
strongly  puffed. 

Alma  Mine,  Floz  4,  West- 
phalia. 
President  Mine,  Dickebank, 
Westphalia. 

Coal  deposits  are  not  at  all  homogeneous,  and  we  can  generally 
distinguish  the  following  components: 

1.  Malting  coal,  jet  black,  brittle,  brilliant,  easily  split  per- 
pendicularly to  its  layers. 

2.  Dull   coal,   brown  to   gray-black,   hardly  any  brilliancy, 
stronger  and  less  brittle.     Is  not  scissile  and  shows  rough  frac- 
ture. 

Malting  coal  is  the  only  constituent  of  sand  and  sinter-coals, 
semi-baking,  and  is  the  principal  constituent  of  the  baking  and 
coking  coals,  while  gas-coal  consists  of  alternate  layers  of  malting 
and  dull-coal.  A  coal  extremely  rich  in  dull  coal  is  called  cannel- 
coal.  Since  the  malting  coal  occurs  in  every  kind  of  coal,  it  is 
self-evident  that  it  has  widely  varying  composition  and  fusibility. 
The  dull  coal  is  usually  richer  in  ash  -and  always  richer  in  hydro- 
gen and  gas  than  the  malting  coal. 

3.  Fibrous  coal  is  widely  distributed  in  all  parts  of  the  coal- 
deposits,  forms  generally  thin  layers,  is  similar  to  charcoal  (there- 
fore called  mineral  charcoal)  is  infusible,  low  in  volatile  matter 
and  is  therefore  detrimental  in  coke  and  gas  production. 

4.  Bituminous  shale,  i.e.  slate  impregnated  with  coal  sub- 
stance, is  frequently  similar  to  cannel-coal.     The  coal  substance 
of  bituminous  slate  is  rich  in  hydrogen.    The  moisture  of  freshly 
mined  coals  varies.     In  air-dry  state  they  contain  from  2  to  4  per 
cent,  sometimes  up  to  8  per  cent  of  water.    The  ash  varies  from 
2  to  20  per  cent.    For  some  special  metallurgical  uses,  the  com- 


184 


HEAT  ENERGY  AND  FUELS 


position  of  the  ash  has  to  be  considered,  as  a  coal  rich  in  sulphur 
or  phosphor  is  detrimental  for  certain  uses. 

TABLE  LXXX. 

ANALYSES    OF    BITUMINOUS    COALS. 


Locality. 

Gas. 

Coke. 

Composition  of  coal  in  Per  cent. 

"si 

il 

_! 

H 

5497 
7098 
6420 
7296 

8392 

7069 
7465 

Yield  in 
Per  cent. 

C 

H 

0 

N 

H2O 

Ash. 

Sulphur 
Per  cent. 

I 

E  a 

a 

Austria: 
Kladus  

59.48 
75.09 
68.80 
77.21 

73.20 
72.38 
89.32 
85.62 
85.90 
79.82 

84.54 

74.46 
78.93 

3.55 
4.51 
3.99 
4.00 

4.93 
4.46 
3.80 
4.65 
4.56 
4.96 

4.77 

5.10 
4.90 

8.89 
8.41 
8.23 
8.32 

19.11 
15.05 
2.71 
5.93 
4.77 
4.79 

4.59 

8.25 
7.24 

1.16 
8.41 
1.36 
1.39 

1.71 
1.56 
1.25 

0.84 

1.52 
1.57 

7.90 
6.08 
5.65 
2.41 

3^00 
1.25 

6.07 
4.36 

19.02 
5.31 
11.97 
6.07 

2.76 
8.11 
4.17 
2.09 
3.21 
5.36 

4.00 

4.08 
1.96 

0^82 

0.49 
1.04 

0^90 
0.68 

Pilsen 

Karwin  
Maehr.  Ostrau 
Germany  : 
Upper  Silesia. 
Saarbriicken  .  . 
Aachen 

70.5 

Essen  
Bochum  
Westphalia.  .  . 
France: 
St.  Etienne  .  .  . 
England  : 
Tyldesley  
Bickershaw.  .. 

19.75 

32.08 
29.81 

69^9 
79.0 

57.75 
63.87 

By  dressing  and  washing,  the  ash-content  can  be  considerably 
decreased. 

Of  technical  importance  is  the  decomposition  of  coal  in  the 
atmosphere  by  absorption  of  oxygen,  which  takes  place  in  two 
stages;  at  first  the  available  hydrogen  and  some  carbon  are 
oxidized  to  water  and  carbon  dioxide ;  in  the  second  stage  oxygen 
is  absorbed  by  the  coal,  but  no  carbon  dioxide  nor  water  escapes, 
so  that  an  increase  in  weight  takes  place,  sometimes  as  much  as 
4  per  cent.  Thereby  not  only  the  thermal  value,  but  also  the 
property  of  caking  and  the  yield  of  coke  is  decreased. 

By  this  absorption  of  oxygen  and  oxidation  the  coal  is  heated, 
sometimes  to  such  a  high  temperature  that  not  only  the  included 
gases  escape  (causing  decrease  in  weight)  but  also  spontaneous 
combustion  can  take  place.  This  spontaneous  combustion 
is  facilitated  by  the  oxidation  of  pyrite,  which  is  present  in  the 


BITUMINOUS  AND  ANTHRACITE  COALS 


185 


coal.     The  gases  included  in  bituminous  coals  vary  in  composi- 
tion as  follows: 

Methane 0  per  cent  to  90  per  cent. 

Carbon  dioxide 0.2  per  cent  to  54  per  cent. 

Oxygen trace  to  17  per  cent. 

Nitrogen 10  per  cent  to  90  per  cent. 

The  quantity  varies  between  18  and  190  cu.  cm.  in  100  g.  of  coal. 


TABLE   LXXXI. 

ANALYSES    OF    BITUMINOUS    COALS.      (G.  Arth.) 

BITUMINOUS   COAL  FROM  THE   FRANKENHOLZ  MINE  WITH  8 . 1  PER  CENT 

OXYGEN. 


C  Per 

H2Per 

Ash. 
Per 

C  Per 

H  Per 

O  Per 

cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

of  Organic 

Compounds. 

Fresh  mined  

2.08 

81.69 

5.79 

8.15 

83.42 

5.91 

After  12  months: 

In  running  water  

1.75 

82.24 

5.70 

7.88 

83.70 

5.80 

In  stagnant  water  

1.82 

82.15 

5.62 

7.94 

83.67 

5.72 

Exposed  to  the  weather  

1.96 

81.45 

5.58 

8.80 

83.08 

5.49  . 

BITUMINOUS     COAL    FROM    DROCOURT    (PAS    DE    CALAIS)    WITH    3.7    PER 

CENT    OXYGEN. 


Fresh  mined  

4.08 

85.06 

5.20 

3.68 

88.68 

5.42 

After  12  months: 

In  running  water  

4.33 

85.70 

5.26 

2.71 

89.58 

5.49 

In  stagnant  water  

4.78 

84.67 

4.87 

3.74 

88.92 

5.11 

Exposed  to  the  weather  

5.77 

82.78 

5.00 

4.54 

87.84 

5.30 

BITUMINOUS    COAL    FROM    AISEAU-PRELE     (CHARLEROI)    WITH     1.6    PER 
CENT    OXYGEN. 


Fresh  mined  

2  86 

89  83 

3  88 

1  59 

92  41 

3  99 

After  12  months: 
In  running  water 

2  64 

89  30 

3  79 

2  61 

91  70 

3  89 

In  stagnant  water 

3  31 

89  01 

3  84 

2  05 

92  05 

3  97 

Exposed  to  the  weather  

3.19 

88.77 

3.99 

2.38 

91.69 

4.05 

186 


HEAT  ENERGY  AND  FUELS 


B.  ANTHRACITE. 

Anthracite  is  the  last  stage  of  carbonaceous  decay.  It  is  black, 
very  hard  and  strong,  has  generally  conchoidal  fracture  (some- 
times it  is  very  slaty),  and  has  a  specific  gravity  of  1.40  to  1.80. 

Anthracite  burns  without  smoke,  with  a  short,  weak,  reddish 
flame.  By  distillation  an  extremely  small  quantity  of  volatile 
matter  is  obtained.  The  composition  of  the  organic  component 
is: 

C  93  to  95  per  cent 
H  4  to  2  per  cent 
0  +  N  3  per  cent 

100  per  cent. 

TABLE   LXXXII. 
ANALYSES    OF   ANTHRACITES. 


1 

Coke 

*J 

"cd 

Gas 

C 

C 

H 

O 

N 

H20 

Ash 

C 
OJ 

> 

Occurrence. 

Per 

Ppr 

Per 

Per 

Per 

Per 

Per 

Per 

IS 

~£  —  : 

Observer. 

cent. 

xcjr 
cent. 

cent. 

cent. 

cent. 

cent. 

cent. 

cent  . 

f£ 

co 

la 

a 

H 

Denver,  Ruby 

Mine,   U.S.A. 

87.56 

3.11 

2.69 

0.  13 

0.72 

4.15 

0.89 

Denver,     An- 

thracite Mine, 

Fischer. 

U.S.A  

..... 

89.49 

3.33 

1.19 

0.66 

0.59 

4.00 

0.78 

Pennsylvania, 

»—  V— 

Wilkesbarre.  .  . 

86.91 

2.80 

3.89 

5.97 

0.43 

Schultze. 

Do  

2.75 

87.90 

86  .  456 

1.995 

1  .  449 

0.  75 

3.45 

5.90 

7484 

P.  Mahler. 

Tonking, 

Kebao  

4.56 

85.  19 

85.746 

2.733 

2.671 

0.60 

2.80 

5.45 

7828 

Do. 

Turacher-Alpe 

Styria  

84.  14 

2.55 

4.18 

4.31 

4.82 

7339 

R.  Schoffel. 

Werchzirm- 

Alpe,   Styria  . 

75.48 

2.05 

3.88 

2.56 

16.03 

6560 

Do. 

The  distillation  yields: 

Powdered  coke 90  to  92  per  cent 

Gas 10  to    8  per  cent 

100  per  cent. 

The  anthracites  are  of  the  greatest  importance  in  America, 
where  they  occur  in  immense  deposits.  They  are  of  no  impor- 
tance in  Europe. 


BITUMINOUS  AND  ANTHRACITE  COALS  187 

Suggestions  for  Lessons. 

Examination  of  various  solid  fuels.  Elementary  and  interme- 
diate analysis,  fuel  tests,  ash  analysis. 

Determination  of  the  density  and  of  the  weight  of  1  cu.  m. 

Examination  of  green  and  seasoned  fuels. 

Determination  of  the  quantity  and  composition  of  the  included 
gases. 


CHAPTER  XIV. 
ARTIFICIAL  SOLID   FUELS. 

FOR  certain  purposes  it  is  advantageous  to  use  fuels  richer  in 
carbon  than  the  ones  occurring  in  nature.  Such  fuels  are  pre- 
pared by  destructive  distillation  of  the  natural  solid  fuels, 
whereby  the  following  products  of  decomposition  are  formed: 
(1)  gases;  (2)  tar;  (3)  tar  water,  and  (4)  residuum  rich  in  carbon. 

The  quality  and  quantity  of  the  products  of  decomposition 
depend  on  the  nature  of  the  raw  material,  temperature  of  decom- 
position and  other  circumstances.  With  increasing  temperature 
the  output  of  gas  increases  both  as  to  weight  and  volume,  but 
simultaneously  the  quantity  of  heavy  hydrocarbons  in  the  gas 
decreases,  and  therefore  also  the  illuminating  power  of  the  gas. 

The  pressure  under  which  the  distillation  is  carried  out  is  also 
of  importance  relative  to  the  products  formed. 

The  advantages  of  producing  carbonized  (coked)  fuels  are: 

1.  A  fuel  of  higher  thermal  value  is  obtained. 

(a)  As  the  carbon-content  of  the  coked  fuel  is  higher  than 
that  of  the  natural  fuel. 

(b)  As  the  volatile  substances  in  spite  of  their  combustibility, 
require  for  their  gasification  a  considerable  amount  of  heat, 
which  is  at  our  disposal  when  we  use  coked  fuels. 

Thereby  the  cost  of  transportation  per  heat  unit  is  decreased. 

2.  Combustion  of  coked  fuels  is  smokeless. 

3.  Coked  fuel  does  not  bake. 

4.  Coked  fuel  contains  less  sulphur  than  does  raw  fuel. 

5.  Under   certain   conditions   valuable   by-products   can   be 
collected.     On  the  other  hand  coking  has  the  following  disad- 
vantages : 

1.  The  carbonizing  (coking)  of  the  natural  fuels  requires  a 
certain  amount  of  heat,  fuel,  wages  and  machinery. 

188 


ARTIFICIAL  SOLID  FUELS  189 

2.  Coked  fuel  burns  with  a  short  flame,  while  for  certain 
operations  a  long  flame  is  essential. 

3.  The  ash-content  is  increased  by  coking. 

Heat  of  formation  of  1  kg.  of  a  fuel  is  the  number  of  calories 
which  were  set  free  by  the  formation  of  such  fuel  from  its  ele- 
ments, and  which  naturally  have  to  be  added  again  for  the 
decomposition  into  the  elements.  Heat  of  decomposition  is 
obtained  by  deducting  the  directly  observed  heat  of  combus- 
tion of  the  fuel  from  the  sum  of  the  heats  of  combustion  of  the 
elementary  components. 

Schwackhofer  found  for  Ostrau  (Austria)  nut  coal: 

C 73.55  per  cent 

H2 4.54  per  cent 

0 11.38  per  cent 

N 0.46  per  cent. 

Hygr.  H20 2.44  per  cent 

Ash 5.63  per  cent 

Combustible  sulphur 0.60  per  cent 

Thermal  value 7433  cal. 

The  heat  of  combustion  of  the  elementary  components  of  this 
coal  are: 

C  0.7355  X  8080  =  5942.84  cal. 
H2  0.0454  X  29,600  -  1343.84  cal. 
S  0.0060  X  2500  -  15.00  cal. 


Total 6301.68  cal. 

Thermal  value  of  coal  deduct    7433.00 


Heat  of  formation  of  1  kg.  coal  -  1131.32  cal. 

For  coal  from  Leoben  (Styria)  Schwackhofer  found: 

C 60.91  per  cent 

H2 4.22  per  cent 

0 17.99  per  cent 

N 0.71  per  cent 

Hygr.  H20 9.92  per  cent 

Ash 6.25  per  cent 

Combustible  sulphur 0.52  per  cent 

Thermal  value.  .  .  6013  cal. 


190 


HEAT  ENERGY  AND  FUELS 


The  heat  of  combustion  for  the  elementary  components  is : 

C 0.6091  X     8080  -  4921.53  cal. 

H 0.0422  X  29,600  =  1249.12  cal. 

S 0.0052  X     2500  -      13.00  cal. 

Total 6183.65  cal. 

Thermal  value  of  coal  deduct 6013 . 00  cal. 

Heat  of  formation  of  1  kg.  coal  +  170 . 65  cal. 

The  heat  necessary  for  gasifying  coal  depends  on  the  nature  of 
the  gasification,  i.e.  the  nature  of  the  products  of  decomposition. 
If  the  gasification  is  effected  by  destructive  distillation,  the  heat 
necessary  equals  the  difference  of  the  heat  of  formation  of  the 
coal  and  the  heat  of  formation  of  the  distillation  products 
(from  the  elements).  The  heat  necessary  for  gasifying  can  also 
be  calculated  by  deducting  the  thermal  value  of  the  distilla- 
tion-products (calorimeter)  from  the  thermal  value  of  the  coal. 

Therefore  the  heat  required  for  the  destructive  distillation  of 
1  kg.  of  this  coal  is  254.792  cal. 

According  to  the  nature  of  the  raw  material,  the  coked  mate- 
rials are  named: 

1.  Charcoal. 

2.  Peat-coal. 

3.  Coke;  to  the  class  of  artificial  fuels  belong  also  the 

4.  Briquettes. 

TABLE  LXXXIII. 
COMPOSITION  AND  PRODUCTS  OF  DESTRUCTIVE  DISTILLATION  OF  COAL. 

(P.  Mahler.) 


Substance. 

Percentage  of  Elementary  Compo- 
sition. 

Ther- 
mal 
Value 
in  Cal. 

Yield 
in  Kg. 
from 
100  Kg. 

of  Coal. 

Thermal 
Value  of 
Products 
in  Cal. 

C 

H2 

O 

N 

Ash 

HaO 

Bitum.  coal  of  Corn- 
men  try  

75.182 

5.176 

8.202 

0.94 

7.05 

3.45 

7423.2 

100 

742326.0 

Coke  
Tar    from    hydraulic 
main  
Tar  from  tar  collector. 
Tar  from  cooler  
Tar  from  condenser  .  .  . 
Gas...  
Ammonia  water  

85.773 

90.186 
89  910 
87.222 
85.183 
55.086 

0.414 

4.848 
4.945 
5.499 
5.599 
21.460 

2.043 

s—  *, 

4. 
5. 
7. 
9 
23. 

0.62 

966 
145 

279 
218 
454 
17g 

10.27 
.  perl 

0.88 
ter  " 

7019.4 

8887.0 
8942.8 
8831.0 
8538.4 
11111.0 

65.66 

3.59 
0.87 
1.46 
1.89 
17  09 
9.36 

460893.8 

31904.3 
7780.2 
10243.9 
16137.6 
189887.0 

Total  
Heat  lost  in  destruc- 
tive distillation  
Coke  used  as  fuel  

7019^ 

99.62 

716846.8 

2K09 

25479.2 
148053.2 

CHAPTER  XV. 
CHARCOAL. 

THE  dry  distillation  of  wood  yields 

(a)  Hygroscopic  water. 

(6)  Illuminating  gas,  consisting  mainly  of 

Acetylene,  C2H2. 

Ethylene,  C2H4. 

Benzol,  C6H6. 

Naphthalene,  C10H8. 

Carbon  Monoxide,  CO. 

Carbon  Dioxide,  C02. 

Methane,  CH4. 

Hydrogen,  H2. 

(c)  Tar,  consisting  of 

Benzol,  C6H6. 
Naphthalene,  C10H8. 
Paraffin,  C20H42  to  C22H46. 
Retene,  C18H18. 
Phenol,  C6H60. 
Oxyphenic  Acid,  C6H602. 
Kresylic  Acid,  C7H80. 
Phlorylic  Acid,  C8H10O. 

fC7H802. 
Creosote  -]  C8H1002. 

(C9H1202. 
Resins 

(d)  Pyroligneous  acid,  consisting  of 

Acetic  Acid,  C2H402. 
Propionic,  Acid,  C3H602. 
Acetone,  C3H60. 
Wood  Alcohol,  CH40. 

(e)  Charcoal. 

191 


192  HEAT  ENERGY  AND  FUELS 

Charcoal  contains,  besides  carbon,  H,  0  and  ash,  and  generally 
also  hygroscopic  water.  The  average  composition  of  air-dry 
charcoal  is 

C  (including  H  and  O)  85  per  cent 

Hygroscopic  H20 12  per  cent 

Ash 3  per  cent 

100  per  cent. 

Tamm  takes  the  average  composition  of  charcoal  as  follows : 

Air-Dry  Perfectly  Dry 

83.0) 

90 . 0  per  cent  13 . 2  [•  98 . 9  per  cent 
2.7) 
1.1 


100.0  100.0 

According  to  the  researches  of  Violette  on  charring  wood,  the 
wood  remains  unchanged  up  to  a  temperature  of  200°  C;  at 
232°  C.  it  gets  brown;  between  270  and  350  °  C.  red  coal  and  at 
400°  C.  black  coal  is  formed. 

The  so-called  red  wood,  which  stands  between  red  and  black 
coal,  has  the  following  composition  (Fresenius) : 

C 52.66  percent 

H 5 . 78  per  cent 

0 36.64  percent 

.     Ash 0 . 43  per  cent 

H20. : 4. 49  per  cent 

100. 00  per  cent. 

Violette 's  researches  comprise  the  following  series: 

1.  Coals  made  at  different  charring  temperatures  (150°  to  over 
1500°  C.)  from  one  kind  of  wood  (Rhamnus  frangula). 

2.  Coals  from  the  same  wood  produced  at  different  tem- 
peratures in  entirely  closed  vessels. 

3.  Coals  from  those  kinds  of  wood  which  are  mainly  used  in 
France  for  gunpowder  manufacture. 

4.  Coals  made  at  300°  C.  from  72  different  varieties  of  wood. 


CHARCOAL 


193 


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194 


HEAT  ENERGY  AND  FUELS 


For  these  experiments  the  wood  was  cut  into  cylindrical 
pieces  of  1  cm.  diameter  and  dried  in  a  current  of  steam  at  150°  C. 
The  charring  (except  in  the  second  series)  was  effected  up  to 
350°  C.  with  superheated  steam,  at  higher  temperature  in  a 
crucible  at  the  melting  point  of  antimony,  copper,  silver,  gold, 
steel,  iron,  and  platinum. 

The  results  of  the  first  series  are  given  in  the  table  on 
page  193. 

TABLE   LXXXV. 
YIELD  OF  COAL  BY  CHARRING.     (Karsten.) 


Kind  of  Wood. 

Rapid 
Distillation. 

Slow  Distillation. 

Karsten. 

Karsten. 

Stolze. 

Winkler. 

Oak  wood,  young  
Oak  wood  old 

16.54 
15.91 
14.87 
14.15 
13.11 
13.65 
14.45 
15.30 
13.05 

12'20 
12.15 
14.25 
14.05 
16.22 
15.35 
15.52 
13.75 
13.30 

25.60 
25.71 
25.87 
26.15 
25.22 
26.45 
25.65 
25.65 
25.05 

24.70 
25.10 
25.25 
25.00 
27.72 
24.75 
26.07 
25.95 
24.60 

|    26.1 
|    24.6 
|    23.8 

24.4 
28.8 
24.4 

|    23.4 
j    21.5 

|    23.7 

22.8 
21.1 
22.2 

22.8 
17.8 

17.6 
17.7 
17.6 

20.6 
20.1 

16.2 
19.4 
15.0 

Red  beech,  young 

Red  beech,  old  
White  beech,  young  
White  beech,  old  
Alder,  young  
Alder,  old  
Birchwood,  young  
Poplar.  .  .  . 

Birchwood,  old  
Birchwood,  well  preserved.  .  .  . 

Red  pine,  young  
Red  pine,  old  

Fir  wood   young 

Fir  wood,  old    . 

Pine,  young.  ... 

Pine,  old  

Linden  
Ash 

Willow. 

13.40 
17.00 

'24!e6' 
27.95 

Rye  straw 

Fern  

The  tests  show  that  quick  coking  yields  only  about  half  as 
much  charcoal  as  slow  coking. 

Violette  obtained  by  charging  wood  into  a  preheated  (432 
degrees)  charring  vessel  about  8.96  per  cent  coal,  while  he 
obtained  18.87  per  cent  by  heating  the  same  kind  of  wood  for 
six  hours  gradually  up  to  432  degrees. 

In  the  second  series  of  Violette's  experiments  the  wood  pieces 
(Rhamnus  frangula)  were  weighed,  dried  at  150°  C.  and  were 
kept  in  closed  glass  tubes  at  constant  temperature  with  super- 
heated steam.  The  results  were : 


CHARCOAL 


195 


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196 


HEAT  ENERGY  AND  FUELS 


The  third  series  of  experiments  with  coals  made  from  different 
kinds  of  wood  showed  the  variable  composition  of  the  charcoal 
obtained.  Violette  found  in  the  interior  part  of  the  apparatus 
coal  with  85  per  cent  carbon,  on  the  walls  with  70  per  cent  of 
carbon. 

In  the  fourth  series  of  experiments  72  kinds  of  wood  were 
dried  for  two  hours  with  steam  of  150°  C.  and  then  charred  for 
three  hours  with  steam  of  300°  C.  The  results  were  as  follows : 

TABLE   LXXXVII. 
YIELD  OF  COAL  BY  CHARRING. 


No. 

Kind  of  Wood  dried  at  150 
Degrees,  Charred  at 
300  Degrees. 

Yield 
of  Coal, 
Per 
cent. 

No. 

Kind  of  Wood  dried  at  150 
Degrees,  Charred  at 
300  Degrees. 

Yield 
of  Coal 
Pei- 
cent. 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
33 
34 
35 
36 

Cork  wood  

62.80 
54.30 
52.00 
52.17 
49.69 
46.99 
46.09 
46.06 
44.89 
44.25 
43.75 
43.07 
41.86 
41.48 
40.95 
40.90 
40.75 
40.64 
40.44 
40.35 
40.31 
39.49 
39.44 
39.22 
38.83 
38.46 
37.93 
37.41 
37.31 
37.27 
37.21 
36.96 
36.60 
36.53 
36.06 
36.01 

37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
58 
59 
60 
61 
62 
63 
64 
65 
66 
67 
68 
69 
70 
71 
72 

Currant  bush  
Medlar  tree  
Cherry  bush  
American  aspen  
Hooded  milfoil  

35.66 
35.57 
35.53 
34.87 
34.85 
34.75 
34.  7C 
34.69 
34.69 
34.59 
34.44 
34.40 
34.28 
34.24 
34.17 
34.06 
33.76 
33.75 
33.74 
33.61 
33.42 
33.36 
33.33 
33.28 
33.28 
32.79 
32.70 
32.21 
32.05 
32.03 
31.88 
31.85 
31.84 
31.33 
31.12 
30.86 

Ebony  
Satinwood  
Willow  (foul)  
Wood  from  Herculaneum  . 
Wheat  straw  
Oak  
Yew  tree  
Mahogany  

Ivy  
Hawthorn  
Plane-tree 

Apple-tree  
Elm-tree  .  .  . 

Beech 

Ironwood  
Juniper  
Pockwood  
Moor  pine  
Poplar  (leaves)  
Poplar  (root)  
Fir  
Fungus  growing  on  willows 
Box 

Hornbeam  . 

Alder-tree  
Barberry  
Furze  
Birch-tree  
Plum-tree 

Sycamore  
Maple  
Willow  
Alder  —  buckthorn  .  .  . 
Virginian  acacia  
Flowery  dogwood  .... 
Broom  
Ash-tree  
Quince-tree  
Hazel-tree  
Bird  cherrv  
Holly-tree*.  
Alaternus  
Guelder-rose  
Pear-tree  
Linden 

Lote-tree 

Bird  cherry  
Palm-tree  
Thuja,  Canadian  
Hemp  stalk 

Virgin's  bower 

Rush  ....  

Cocoanut-tree  
Carded  cotton  
Elder-tree 

Varnish-tree  
Rose-tree  (wild)  
Honeysuckle 

Spindle-tree 

Lilac  
Begonia  
Poplar  

Vine  
Chestnut  
Bean  trefoil  

Horse-chestnut  

CHARCOAL  197 

The  conclusions  that  can  be  drawn  from  Violette's  experi- 
ments are : 

1.  Wood  yields  less  coal  the  higher  the  temperature.     For 
the  same  kind  of  fuel  the  yield  for  instance  is : 

At    250°  C 50  per  cent  weight, 

At    300°  C 33  per  cent  weight, 

At    400°  C 20  per  cent  weight, 

At  1500°  C 15  per  cent  weight. 

2.  From  woods  treated  at  the  same  temperature  the  yield  of 
coal  is  proportional  to  the  time  of  distillation.    With  slow  dis- 
tillation the  yield  is  twice  as  great  as  with  quick  distillation. 

3.  The  carbon  content  of  the  coal  is  proportional  to  the  tem- 
perature of  distillation ;  the  coal  contains  for  instance : 

At    250°  C 65  per  cent, 

At    300°  C 73  per  cent, 

At    400°  C 80  per  cent, 

At  1500°  C 96  per  cent. 

4.  By  distillation  in  perfectly  closed  vessels  very  little  carbon 
is  gasified,  as  most  of  the  carbon  is  retained  in  the  coal  in  solid 
form  on  account  of  the  increased  pressure.    This  explains  the 
higher  yield  in  retorts  as  compared  to  pile-charring. 

5.  The  charring  of  wood  in  perfectly  closed  vessels  yields  at 
280°  C.  80  per  cent  of  red  coal,  while  by  means  of  superheated 
steam  only  40  per  cent  can  be  obtained.    This  is  due  to  the 
increased  pressure,  which  changes  the  equilibrium  towards  a 
smaller  volume. 

6.  In  perfectly  closed  vessels  wood  melts  at  from  300  to  400°  C. 
under  formation  of  a  black,  brilliant  mass,  without  any  organic 
structure,  similar  to  melted  pitch-coal. 

7.  Coals  produced  in  cylinders  or  iron  pots  are  of  variable 
composition  (70  to  84  per  cent  C.),  while  with  superheated  steam 

-  according  to  temperature  —  coal  of  any  constant  composition 
can  be  made. 

The  red  coal  used  in  gunpowder  manufacture  is  nothing  but 
half-charred  wood  of  red-brown  or  brown-black  color.  It  burns 
with  a  long  illuminant  flame  and  therefore  contains  less  carbon 
and  more  hydrogen  than  charcoal  proper  (black  coal). 


198 


HEAT  ENERGY  AND  FUELS 


Good  charcoal  is  black  in  color  with  a  steel-blue  lustre.  It 
has  a  distinct  wood  structure,  conchoidal  fracture,  low  specific 
gravity  (0.17  to  0.24),  is  fairly  strong,  easily  ignited,  and  burns 
with  a  very  short,  blue,  smokeless  flame. 

By  lying  in  the  atmosphere  charcoal  absorbs  about  10  per 
cent  of  water;  if  moistened  directly  with  water,  50  per  cent  is 
absorbed. 


WEIGHT  OF  CHARCOALS  (Petraschek). 


Charcoal. 

100  Liters 
Weigh,  Kg. 

From  soft  wood,  average  
From  hard  wood,  average..  .  . 

17 
24 

Hard  and  soft  wood  mixed.  .  . 

21 

The  loss  of  volume  of  charcoal  during  transportation,  etc.,  by 
breakage  and  friction  is,  according  to  Wessely : 


Decrease  in  Volume. 
Per  cent. 

Carting. 

Sleighing. 

Hours 
road. 
1  

according    to    quality    of 

Limits.    Average. 
3-8              5£ 

Limits.  Average. 
3-6              5 

2 

Il—Ql                  9i 

11_Q                      94 

3     . 

1-3              2 

1  24             ll 

4... 

1-2              H 

1-1  4-             U 

One  volume  of  charcoal  from  boxwood  absorbs  the  following 
quantities  of  gas  (Saussure) : 


NH3 90vol.  I 

HC1 85vol.  ' 

S02 65vol. 

H2S 55vol. 

N02 40vol. 

C2H4 35vol. 


CO, 


35      vol. 


CO 9.42  vol. 

O 9.25vol. 

N 7.50vol. 

CH4 5.00vol. 

H2 1.75  vol. 


0.59  g.  of  different  kinds  of  coal  absorb  the  quantities  of  dif- 
ferent gases  (in  cu.  cm.)  given  in  Table  LXXXVIII. 


CHARCOAL 


199 


TABLE   LXXXVIII. 

ABSORBING   CAPACITY   OF  COALS. 


Gases. 

Charcoal. 

Peat. 

Bone 
Black. 

NH 

98  5 

96  0 

43  5 

HC1  

TT    0 

45.0 
30  0 

60.0 
28.5 

9.0 

COo 

14.0 

10.0 

5.0 

o              

0.8 

0.6 

0.5 

SO2             

32.5 

27.5 

17.5 

The  temperature  of  ignition  depends  on  the  temperature  of 
distillation  as  shown  in  Table  LXXXIX. 


TABLE  LXXXIX. 
TEMPERATURE  OF  IGNITION  OF  CHARCOAL   (Violette). 


Temperature  of  Charring. 

Temperature  of  Ignition. 

300°  G. 

360-380°  C. 

260-280°  C. 

340-360°  C. 

290-350°  C. 

360-370°  C. 

432°  C. 

400°  C. 

1000-1500°  C. 

600-800°  C. 

Melting  point  of  plati- 

1250°C. 

num. 

We  can  classify  as  follows  the  different  methods  of  producing 
charcoal. 


A.  Charring  in  the 
woods  or  carbon- 
izing under  mov- 
able cover  (with 
changeable  volume 
of  the  charring  ap- 
paratus). 


B.  Charring  in  ap- 
paratus with  con- 
stant volume  of 
the  charring  space. 


(a)  Without  re- 
covery of  by- 
products. 

(6)  With  recov- 
ery of  by-prod- 
ucts. 


(a)  Pile-charring 
(the  heat  re- 
quired is  gen- 
erated in  the 
interior  of  the 
coking  space). 

(6)  The  heat  for 
charring  is  fur- 
n  i  s  h  e  d  from 
outside. 


(a)   in  pits. 


(a)   in  pits. 
(^)  in  piles. 

(a)  The  heat  necessary  for  char- 
ring is  furnished  by  partly 
burning  the  wood  to  be  charred 
(piles  with  admission  of  air  to 
the  interior). 

(/?)  The  heat  necessary  for  char- 
ring is  furnished  by  combustion 
by  gases  free  of  oxygen  (piles 
with  admission  of  combustion 
gases  free  of  oxygen  to  the 
interior). 

(7)  The  heat  is  furnished  by 
superheated  steam. 


200 


HEAT  ENERGY  AND  FUELS 


A.  Charring  in  the  woods, 
(a)  Charring  without  recovery  of  by-products, 
(a)  Charring  in  pits. 

The  pits  are  about  1  m.  deep,  2  m.  wide  at  the  top, 
somewhat  narrower  at  the  bottom.  The  fire  is  started 
with  brushwood,  then  the  wood  is  piled  up  and  cov- 
ered with  earth.  The  coal  is  light  and  unequally 
burned. 
(/?J  Charring  in  round  piles. 

These  piles  have  generally  the  form  of  a  paraboloid, 
and  their  cubic  content  is  calculated  according  to  the 
formula 

d2n    h      d2hn 

T'  2~~T 

or,  as  on  the  finished  pile,  the  circumference  can  be  figured  more 
easily  than  the  diameter: 

u2    7i    h      u2h        u2  h 

7?'  4'2  =  8~x  =  25.31 ' 

As,  however,  the  shape  of  the  piles  is  not  exactly  like  a  para- 
boloid, from  4  to  6  per  cent  is  deducted  from  the  volume  calcu- 
lated according  to  above  formula. 

The  following  varieties  of  wood  are  mainly  used  for  charring 
in  piles: — of  coniferous  trees:  pine,  fir,  red  pine,  and  larch;  of 
leaved  wood:  oak,  red  beech,  white  beech,  ash,  elm,  alder,  and 
birch.  The  most  favorable  age  of  trees  for  charring  is  given  in 

Table  XC. 

TABLE  XC. 

PROPER  AGE  OF  TREES  FOR  CHARRING.  (Scheerer.) 


Wood. 

Age  of  most  Per- 
fect Development. 

Age  at  which  Tree 
can  be  cut. 

Pine  

140 

80  to   100 

Red  pine  
Fir  

150 
80  to  100 

70  to     80 
60 

Larch  .  . 

80  to     90 

50 

Oak  . 

200  to  250 

50  to     60 

Red  beech  
White  beech  
Elm 

|      120  to  140 

80 

120 
20  to     30 

Alder... 

18  to     20 

Birch  

40 

20 

CHARCOAL  201 

In  winter  time  the  wood  contains  less  moisture  than  in  sum- 
mer; winter  is  therefore  the  most  favorable  time  for  cutting  the 
wood.  For  the  erection  of  piles,  locations  are  selected  that  are 
protected  from  wind,  and  a  ground  not  too  dry  and  not  too  wet. 
A  dry  ground  will  break  and  crack,  allowing  too  much  air  to  enter 
into  the  pile.  A  wet  ground  generates  steam,  which,  with  the 
glowing  coal,  is  decomposed  into  hydrogen  and  carbon  dioxide. 
In  both  cases  a  loss  of  coal  results.  The  foundation  ground  of 
the  pile,  which  is  a  little  inclined  towards  the  center,  is  first  of  all 
covered  with  a  layer  of  culm  coal,  In  the  center  a  strong, 
straight  post  (center  pole)  is  driven  into  the  ground  (Slavic  piles, 
Figs.  32  and  33),  or  three  posts  of  even  length  are  driven  in, 
forming  an  equilateral  triangle,  the  length  of  the  sides  being 
about  20  cm.  These  three  posts  form  the  center  shaft  (Italian 
piles,  Fig.  34).  Logs  are  now  laid  around  the  center  of  the 
charcoal  kiln  (pile),  either  vertical  as  in  Fig.  34,  or  horizontal,  or 
both  ways  combined,  as  shown  in  Fig.  33.  Depending  on  the 
size  of  the  pile,  one,  two,  or  more  layers  of  logs  are  put  together, 
the  upper  layer  always  being  less  steep  than  the  lower.  Small 
logs  are  used  to  fill  the  spaces  between  the  large  logs.  The 
upper  layer  is  covered  with  small  logs  and  small  pieces  of  wood, 
for  rounding  the  shape  of  the  pile  (peak  of  the  pile).  In  piles 
with  center  shafts  the  logs  are  always  vertical,  except  the  dome, 
which  consists  of  horizontal  logs.  In  these  piles  the  center  shaft 
is  used  for  starting  the  fire,  while  in  piles  with  a  center  post  a 
channel  is  left  open  for  this  purpose  on  one  side  of  the  bottom 
part,  extending  to  the  center.  The  pile  is  then  covered  on  the 
outside  with  branch  wood,  then  with  leaves  and  grass  (smoke 
cover),  and  at  last  with  earth,  sand,  and  coal  culm  (earth  cover). 
This  cover  does  not  reach  to  the  ground  (Fig.  32,  C,  D),  but  is 
supported  by  timber.  For  starting  the  fire  some  kindling  wood 
is  put  in  on  the  bottom  at  the  center. 

The  fire  is  started  by  inserting  glowing  coal  in  the  kindling 
wood  through  the  center  shaft  or  through  the  above-mentioned 
channel.  Then  the  shaft  is  filled  with  small  pieces  of  wood  and 
covered.  The  fire  now  extends  upwards  and  to  the  sides;  the 
hygroscopic  water  is  evaporated  and  condenses  again  on  the  sur- 
face of  the  pile  (the  pile  sweats) .  Then  acid  gases  and  later  com- 
bustible gases  escape,  and  wherever  they  get  mixed  with  air  an 
explosion  takes  place,  throwing  off  parts  of  the  cover  or  parts  of 


202 


HEAT  ENERGY  AND  FUELS 


D 


D 


FIG.  32.  —  Slavic  Pile. 


FIG.  33.  —  Slavic  Pile. 


FIG.  34.  —  Italian  Pile. 


CHARCOAL  203 

the  pile.  Such  damage  to  the  pile  has  to  be  repaired  instantly. 
This  first  period  of  charring  lasts  from  18  to  24  hours. 

Meanwhile  the  center  shaft  is  burned  out  and  pieces  of  wood 
have  to  be  filled  in  again  and  again  until  the  period  of  sweating 
is  over.  The  bottom  of  the  pile  is  now  also  covered,  and  by  mak- 
ing openings  into  the  cover  (driving  the  pile)  the  fire  is  drawn 
gradually  to  the  lowest  parts.  The  upper  openings  are  closed 
as  soon  as  blue  smoke  starts  to  escape,  the  lower  as  soon  as  the 
flame  shoots  through. 

The  " drawing"  of  the  coal  is  performed  by  removing  the  cover 
on  one  side  and  cooling  the  hot  coal  with  cold  water. 

The  coal  is  marketed  in  the  following  sizes : 

(1)  Lump  coal;  (2)  blacksmith  coal;  (3)  small  size;  (4)  culm; 
(5)  half-charred  wood. 

According  to  the  size  of  the  pile  (120  to  300  cu.  m.)  the  process 
of  charring  requires  from  15  to  20  days. 

Probably  the  largest  pile  kilns  are  operated  at  Neuberg 
(Styria,  Austria).  They  are  built  up  to  400  to  430  cu.  m. 
capacity,  the  500  cu.  m.  size  having  been  abandoned  on  account 
of  difficulty  of  regulation.  Red  pine  and  red  beech  are  charred 
at  Neuberg  in  separate  piles.  The  following  data,  gathered  from 
these  plants  might  be  of  interest: 

1  cu.  m.  hard  wood  half  dry  weighs 550  kg. 

1  cu.  m.  soft  wood  half  dry  weighs 400  kg. 

1  cu.  m.  (cord  wood)  hard  wood  green  weighs 900  kg. 

1  cu.  m.  (cord  wood)  hard  wood  half  dry  weighs 700  kg. 

1  cu.  m.  (cord  wood)  hard  wood  dry  weighs 580  kg. 

1  cu.  m.  (cord  wood)  soft  wood  green  weighs 800  kg. 

1  cu.  m.  (cord  wood)  soft  wood  half  dry  weighs 600  kg. 

1  cu.  m.  (cord  wood)  soft  wood  dry  weighs 400  kg. 

100  liters  hard  coal  weighs 23  kg. 

100  liters  soft  coal  weighs 14  kg. 

The  piles  have  a  diameter  of  14  m.,  a  height  of  4.7  m.,  and  a 
cubic  content  of  400  cu.  m.  of  wood.  They  are  built  with  five 
layers  of  log  wood  of  1  m.  height.  The  yield  of  such  a  pile  is 

Piece  coal  (large  pieces) . . .  2000  hectoliters  )  60  per  cent  volume 
Piece  coal  (small  pieces) .  .  400  hectoliters  J  of  the  wood, 

Culm 1  per  cent, 

Half-charred  wood 1  per  cent. 


204 


HEAT  ENERGY  AND  FUELS 


TABLE   XCI. 

COMPOSITION   OF  KILN  GASES.      (Ebelmen.) 


Composition  in  Per  Cent. 

No. 

Hours  after 
Starting. 

Appearance  of  Gas. 

(Volume.) 

C02 

CO 

K, 

N2 

, 

48 

white  opaque  

25.57 

8.68 

9.13 

56.62 

2 

72 

white  opaque  

26.68 

9.25 

10.97 

53.40 

3 

96 

white  opaque  

27.23 

7.67 

11.64 

53.46 

4 

66 

white  transparent  

23.51 

5.00 

4.89 

66.60 

5 

71 

fairly  transparent  

23.28 

5.88 

13.53 

57.31 

6 

95 

bluish  and  transparent  

23.08 

6.04 

14.11 

55.77 

The  time  required  is : 

Erection  of  pile 4  days, 

Starting  fire. \  hour, 

Charring  process 18-28  days, 

Removing  charcoal 4  days. 

In  working  shifts : 

Erection  4  days  per  10  men 40  shifts, 

Covering  with  branch  wood  1  day  per  2  men 2  shifts, 

Covering  with  leaves 2  shifts, 

Covering  with  earth  1  day  per  12  men 12  shifts, 

Charring,  average 8  shifts, 

Removing  charcoal  4  days  per  8  men 32  shifts, 

Preparing  ground 2  shifts, 

Night-watch  (average) 2  shifts, 


100  shifts. 

The  temperature  of  the  escaping  gas  right  below  the  cover 
was  from  230  to  260°  C.  One  liter  of  same  showed  the  following 
content  of  condensable  products  (tar,  water,  etc.) : 

1.  White  and  opaque 0.987  g. 

2.  Similar  to  A 1.068  g. 

3.  Bluish  and  transparent 0.531  g. 

(/?,)  Charring  in  rectangular  piles. 


CHARCOAL  205 

The  horizontal  piles  are  not  circular  but  oblong,  generally 
having  a  length  of  from  9.5  m.  to  12.5  m.  and  a  width  of  from  2 
to  3  m.  (Fig.  35).  They  are  surrounded  by  posts  which  are 
connected  by  timbers.  The  logs  are  put  in  perpendicular  to  the 


FIG.  35.  —  Rectangular  Pile. 

longitudinal  axis  of  the  pile.  The  hollow  spaces  are  filled  out 
with  branch  wood.  The  height  in  front  is  about  0.6  and 
increases  towards  the  back  part  at  an  angle  of  from  15  to  20 
degrees.  The  fire  is  started  in  the  front  and  goes  slowly  through 
the  entire  length  of  the  pile. 

(6)  Charring  in  the  woods  with  recovery  of  by-products. 
(a)  When  charring  in  pits  a  vessel  covered  with  a  grate  is 

put  on  the  bottom  for  collecting  the  tar. 
(/?)  In  pile-charring  (for  recovering  by-products)  iron  pipes 

are  put  into  the  cover,  leading  to  a  condensing  chamber. 

This  is  done  24-36  hours  after  starting  the  fire,  as  in  the 

first  period  almost  nothing  but  steam  escapes. 

Fig.  36  shows  a  French  pile  with  a  channel  leading  to  a  tar- 
collecting  vessel.    About  20  per  cent  of  tar  is  obtained. 

B.     Charring  in  apparatus  with  constant  volume  of  the 

charring  space. 
(a)  Pile-charring. 

(a)  The  heat  necessary  for  charring  is  furnished  by  partly 
burning  the  wood  to  be  charred  (piles  with  admission  of 
air  to  the  interior). 


206 


HEAT  ENERGY  AND  FUELS 


As  an  example  we  will  describe  the  round  pile  oven  (kiln), 
Fig.  37,  which  has  a  grate  on  the  bottom  for  the  admission  of  air, 
the  quantity  of  the  latter  being  regulated  by  means  of  the  ash- 


FIG.  36.  —  French  Pile. 

door.  The  wood  is  charged  first  through  the  main  door,  then 
through  the  upper  charging-chute.  After  starting  the  fire  the 
main  door  is  closed  with  bricks  and  mortar  and  as  soon  as  steam 


.    .    •• 


FIG.  37.  —  Round  Pile  Oven. 


and  tar  begin  to  escape,  the  upper  charging-chute  is  also  closed, 
so  that  the  escaping  gases  have  to  go  through  the  pipe  shown  at 
one  side  of  the  cover  (dome)  to  the  condensing  vessels.  When 
the  oven  is  sufficiently  heated,  the  ash-door  is  closed.  When 


CHARCOAL. 


207 


the  charring  is  finished,  the  oven  is  allowed  to  cool  and  the  coal 
removed  through  the  main  door. 

(/?)  Charring  in  pile-oven  with   admission  of   combustion 
gases  free  of  oxygen  to  the  interior. 

Such  an  oven  was  built  by  Grill  for  the  iron  works  in  Dalfors 
(Sweden),  Figs.  38  and  39.     It  is  rectangular  and  provided  with 


Stack 


FIGS.  38  and  39.  —  Grill's  Pile  Oven. 


charging  openings  on  both  short  sides.  The  gases  of  combustion 
rise  from  a  fireplace  below  the  oven,  pass  vertically  through  the 
center  of  the  oven  and  escape  in  four  directions  through  side- 
flues.  The  volatile  products  of  distillation  escape  through  two 


208 


HEAT  ENERGY  AND  FUELS 


channels  arranged  in  opposite  corners,  and  pass  through  iron- 
pipes  to  a  tar-collecting  vessel,  the  stack  being  arranged  above 
this  vessel.  After  getting-  the  fire  up,  the  oven  is  closed  tight. 
A  charge  consists  of  172.26  cu.  m.  of  wood;  37.58  cu.  m.  of  wood 
are  used  for  heating;  the  yield  is  147.31  cu.  m.  charcoal.  The 
wages  per  cu.  m.  of  charcoal  at  this  plant  are  6.25  cents. 

The  Schwartz  oven  is  of  similar  construction,  Figs.  40  and  41. 
It  is  provided  with  two  fireplaces  in  the  middle  of  its  length,  and 


Fireplace 
FIGS.  40  and  41.  —  Schwartz  Oven. 


with  two  flues  in  the  middle  of  the  short  sides,  whereby  a  more 
uniform  heat  is  obtained. 

(?-)  Heating  by  means  of  superheated  steam  (Fig.  42). 

This  process,  which  was  introduced  by  Violette  for  the  manu- 
facture of  red  coal  (gunpowder  coal),  yields  about  36  J  per  cent 
of  red  coal  and  no  black  coal,  and  is  therefore  very  much  superior 
to  the  old  process  by  which  14.18  per  cent  red  coal  and  17.81  per 
cent  black  coal  (total  31.99  per  cent)  is  obtained.  Fig.  42  shows 
a  longitudinal  section.  Steam  from  a  boiler  is  led  through  a  coil 
located  in  the  oven.  By  the  direct  fire  the  steam  in  the  coil  is 


CHARCOAL 


209 


superheated.  The  fire  gases  play  around  the  retort  and  escape 
through  the  flue.  The  superheated  steam  from  the  coil  enters 
the  sheet-iron  cylinder  (retort),  which  is  closed  in  front  with  a 
wrought-iron  cover,  and  then  passes  into  the  inner  cylinder, 
which  is  charged  with  the  wood  to  be  charred.  Steam  and 


FIG.  42.  —  Charring  with  Superheated  Steam. 


FIG.  43.  —  Section  through  French  Oven  heated  from  the  Outside. 

products '  of  distillation  escape  through  a  pipe  into  the  atmos- 
phere or  into  a  suitable  condensing  apparatus.  Opposite  the 
entrance  of  steam  a  baffle-plate  is  provided  for  distributing  the 
steam. 

(6)  Charring  by  heat  supplied  from  the  outside. 


210 


HEAT  ENERGY  AND  FUEL 


FIGS.  44-47.  —  Pile  Retort  Oven. 


FIGS.  48-52.  —  Ovens  with  Horizontal  Retorts. 


CHARCOAL 


211 


Charring  is  performed  in  retorts  or  large  cylindrical  vessels. 
In  Russia,  vertical  sheet-iron  cylinders  are  used,  having  a  cubic 
content  of  about  8  cu.  m. :  a  special  fireplace  is  provided  for  heat- 


FIG.  53.  —  Longitudinal  Section  of  a  Modern  Charring  Plant  with  Vertical  Retorts. 

ing  the  vertical  shell.  For  quickly  preheating  the  wood  to  100 
degrees,  steam  is  admitted  at  the  bottom  of  the  cylinder.  The 
tar  flows  through  a  pipe  arranged  at  the  bottom,  to  a  collecting 


FIG.  54.  —  Cross-section  of  a  Modern  Charring  Plant  with  Vertical  Retorts. 

vessel,  while  the  vapors  leave  through  a  pipe  on  the  top,  and  go 
to  a  condensing  apparatus,  from  which  the  condensed  tar  passes 
to  the  above-mentioned  collecting  vessel.  The  products  of  dis- 


212 


HEAT  ENERGY  AND  FUEL 


tillation  pass  through  a  cooled  pipe,  while  the  combustible  gases 
are  lead  back  into  the  fire. 


FIG.  55.  —  Plan  of  a  Modern  Charring  Plant  with  Vertical  Retorts. 

Fig.  43  shows  a  vertical  section  through  a  French  oven  of  simi- 
lar type.  Vertical,  horizontal  and  inclined  retorts  are  used  with 
equal  success  for  charring  wood. 

At  present  pile  ovens  are  used 
only  for  certain  purposes,  as,  for 
instance,  for  charring  pine  wood, 
where  the  recovery  of  the  valuable 
Swedish  tar  and  pine  oil  more  than 
pays  for  the  loss  of  wood-alcohol 
and  acetate  of  lime. 

Modern  pile  ovens  are  built  of 
sheet  iron  for  avoiding  the  loss 
through  brickwork. 

Such  a  modern  pile-retort  oven 
is  shown  in  Figs.  44  to  47.  In  the 
fireplace  the  grate  e  (Fig.  46)  and 
the  arch  dd  (Fig.  44)  can  be  seen. 
Through  the  arch  the  fire  gases  go 
into  the  pipes  /,  while  another  part 
of  the  fire  gases  goes  upwards  near 
the  arch  and  enters  the  pipes,  e. 


YIG.  56.  —  Modern   Charring   Plant 
with  Vertical  Retorts. 


FIG. 


7.  —  Oven    with   Stationary 
Permanent  Retorts. 


All  these  vertical  pipes  go 


CHARCOAL  213 

through  the  interior  of  the  pile-retort.  The  doors  bb  are  used 
for  discharging. 

Similar  ovens  with  horizontal  retorts  are  shown  in  Figs.  48 
to  52.  Figs.  53  to  56  show  a  modern  charring  plant  with  verti- 
cal retorts.  The  retorts  a  can  be  lifted  out  of  the  furnace  by  a 
crane  g,  and  can  be  brought  to  a  suitable  place  for  charging  or 
discharging.  Fig.  57  shows  an  oven  where  the  retorts  remain  in 
permanently;  they  are  discharged  into  small  cars  that  can  be 
moved  right  under  the  retorts. 

To  the  rotary  retort,  however,  belongs  the  future  of  the  char- 
coal industry. 

The  increase  of  the  charcoal  industry  is  shown  by  the  following 
figures,  which  relate  to  this  industry  in  Austria-Hungary: 

About  30  years  ago  the  output  of  charcoal  was  about  10,000 
cu.  m.,  ten  years  later  120,000  cu.  m.,  and  today  it  is  350-400,000 
cu.  m.  per  year. 

For  the  prosperity  of  forestry  this  industry  is  of  the  greatest 
importance,  as  only  hereby  are  we  enabled  thoroughly  to  utilize 
widely  distributed  forests  (by  the  utilization  of  refuse  wood). 


CHAPTER  XVI. 


PEAT-COAL,  COKE   AND   BRIQUETTES. 

THE  destructive  distillation  of  peat,  lignite  or  coal  yields : 
(1)  gases,  (2)  tar,  (3)  tar  water,  and  (4)  a  solid  residue  very 
high  in  carbon,  which,  depending  on  the  raw  material  used,  is 
called  peat  coal  or  coke. 

For  conveying  an  idea  of  the  process  of  destructive  distillation, 
we  give  below  tables  for  the  two  extreme  cases  (peat  and  bitu- 
minous coal). 

DESTRUCTIVE  DISTILLATION  OF  PEAT.     (H.  Vohl.) 

100  parts  of  peat  of  a  Swiss  bog  yielded  by  destructive  dis- 
tillation : 

r  Heavy  Hydrocarbons,  CnH2n 
I  Methan,  CH4 
I  Hydrogen,  H2 
I  Carbon  Monoxide,  CO 
[Tar  0.820  sp.  g. 
1  Heavy  Oil  0.855  sp.  g. 
I  Paraffin 

Ammonia 

Methylamin 

Picolin 

Lutidin 

Anilin 

Caespidin 

"C02 

H2S 

CyH 

Acetic  Acid 

Propionic  Acid 

Butyric  Acid 

Valerianic  Acid 

Phenol 


17. 625  gas 


5. 375  tar 


25. 00  tar  water 


bases 


acids  - 


.  water 


25.00  peat  coal 


214 


PEAT-COAL,  COKE  AND  BRIQUETTES  215 

% 

DESTRUCTIVE  DISTILLATION  OF  BITUMINOUS  COAL. 

(R.  Wagner.) 
100  parts  gas  coal  of  the  following  composition : 

C 78.0  per  cent 

Disposable  H2 4.0  per  cent 

N 1.5  per  cent 

S 0.8  per  cent 

H20  chemic  combined 5.7  per  cent 

H20  hygroscopic 5.0  per  cent 

Ash 5.0  per  cent 


100.0  per  cent. 
Products  of  dry  distillation  : 


1.   70-75  parts  of  coke  j  !f^°n  T^-T  g  ^^  °'  ° 

I  Fe7S8  and  earthy  matters,       10-  5% 


2.  Tar  water  (ammonia  water)  containing 

(a)  Main  components  (water,  carbonate  of  ammonia  and 

sulphide  of  ammonia). 
(ft)  Additional    components  (chloride,  cyanide  and  sulfo- 

cyanide  of  ammonia). 

3.  Tar,  containing: 

(a)  Liquid   hydrocarbons    (Benzol,   Tolnol,    Pseudocumol, 

Cyanol,  Propyl,  Butyl,  etc.). 

(ft)  Solid  hydrocarbons  (Naphthalin,  Acetylnaphthalin,  An- 
thracen,  Reten,  Chrysen,  Pyren). 

(?)  Substances  containing  oxygen  (Phenol,  Kresol,  Phlorol, 
Rosolic  Acid,  Oxyphenolic  Acid,  Creosote,  Pyridin,  Anilin, 
Picolin,  Lutidin,  Collidin,  Leukolin,  Iridolin,  Akridin). 

(d)  Asphaltic  substances  (Anthracen,  Resins,  Coal). 

4.  Illuminating  Gas  : 

{Gases  :  Acetylen,  Ethylen,  Propylen,  Bu- 
Trtylen'    -D        i 
Vapors:     Benzol,    Styrol,    Naphthalin, 
Acetylnaphthalin,  Propyl,  Butyl. 


216 


HEAT  ENERGY  AND  FUELS 


(/?)  Diluting  parts  (Hydrogen,  Methane,  Carbon  Monoxide). 

(7-)  Impurities  (Carbon  dioxide,  Ammonia,  Cyanogen,  Rho- 
dan,  Sulfuretted  Hydrogen,  Sulfuretted  Hydrocarbons, 
Bisulphide  of  Carbon,  Nitrogen). 

The  manner  in  which  the  distillation  proceeds  and  the 
quantity  and  composition  of  the  various  products  are  distinctly 
affected  by  other  factors  than  the  character  of  the  raw  mate- 
rials. The  most  important  of  these  factors  is  the  gasifying 
temperature. 

L.  T.  Wright  has  distilled  at  different  temperatures  a  coal  of 
the  following  composition: 

C 75 . 71  per  cent, 

H2 6 . 27  per  cent, 

S 1 . 72  per  cent, 

N 1.72  percent, 

0 11 . 59  per  cent, 

Ash 2 . 99  per  cent, 


100. 00  per  cent. 

The  yield  of  100  kg.  of  coal  at  a  gasifying  temperature  of  800°  C. 
is  given  in  Table  XCII. 


TABLE  XCII. 

ANALYSIS  OF  DESTRUCTIVE  DISTILLATION  PRODUCTS. 


100  Kg.  Coal 

C 

H2 

S 

N 

O 

Ash. 

Yielded. 

K 

?. 

Coke  
Tar   .  .  . 

57.38 
6  11 

1.24 
0  46 

1.05 
0  05 

1.06 
0  06 

1.28 
0  60 

2.96 

64.97 

7  28 

e!43 

Gas  water  
Gas  

0.08 

7  56 

1.06 

2.85 

0.12 
trace 

0.22 
0.36 

8.30 
1.46 

9.78 
12.23 

9.78 
21140.0 

In  purifying  mass 

0.22 

0.02 

0.39 

0.56 

0.56 

1.20 

Total  

71.35 

5.63 

1.61 

1.71 

12.20 

2.96 

95.46 

PEAT-COAL,   COKE  AND   BRIQUETTES 


217 


The  yield  obtained  at  a  temperature  of  1100°  C.  is  given  in 
Table  XCIII. 

TABLE   XCIII. 
ANALYSIS  OF  DESTRUCTIVE  DISTILLATION  PRODUCTS. 


100  Kg.  Coal 
Yielded. 


H2 


Ash. 


Kg. 


Total. 


Liters. 


Coke 

Tar 

Gas  water 

Gas 

In  purifying  mass 

Total . . 


57.95 
4.78 
0.08 
8.53 
0.38 


71.73 


0.70 
0.38 
1.06 
3.42 
0.04 


5.61 


0.77 
0.06 
0.13 
trace 
0.74 


1.70 


0.47 
0.05 
0.21 
0.86 
0.02 


1.61 


1.24 
1.18 
8.30 
2.30 
0.93 


13.95 


2.97 


64.10 
6.47 
9.78 

15.11 
2.11 


5.37 
9.66 
31200.0 


2.97 


97.57 


At  800°  C. 


At  1100°  C. 


There  was  further 

Soot  in  tar 

Specific  gravity  of  gas  water 

Illuminating  power   of  gas   at   an 
hourly  use  of  150  liters 


15  per  cent 
1.0 

18  candles 


25-30  per  cent 
1.2 

15.3  candles 


A  further  comparison  shows: 


At  800°  C. 


At  1100°C. 


Coke 

Tar 

Gas  water, 
Gas.  . 


64.75  kg. 

6.43  1. 

9.78  1. 
21.14cu.  m. 


64.16  kg. 

5.371. 

9.961. 
31.20cu.  m. 


With  increasing  temperature  the  gas  quantity  (volume),  the 
specific  gravity  of  the  tar,  and  its  content  of  soot,  increase,  while 
the  crude  naphtha  and,  especially  on  light  tar  oil,  content  of  tar 
considerably  decrease. 

With  increasing  temperature  the  creosote  and  anthracen  oil 
content  decreases,  while  the  pitch  content  increases.  The 
sulphur  content  of  the  gas  other  than  that  in  the  form  of  H2S  is 
three  times  as  great  at  the  high  as  at  the  low  temperature.  The 
ammonia  content  is  small  at  low  temperature,  is  a  maximum  at 
medium  and  decreases  with  temperature  rise  at  high  temperature. 


218 


HEAT  ENERGY  AND  FUELS 


The  course  of  distillation  is  different  at  the  beginning  and  at 
the  end.  In  the  Paris  gas  plant  at  a  temperature  of  1000°  C. 
there  is  obtained : 

Time  of  distillation,  hrs.O      1  2  3  456 

Volume  of  gas 0     17         30         27         20         6       0 

Ilium,  power  per  1051... 0       1.15      0.90      0.30      0.10    0.4    0 

C.  G.  Miller  divides  the  time  of  distillation  into  two  periods: 
In  the  first  —  the  period  of  distillation  proper  —  at  the  com- 
paratively low  temperature  of  500°-600°  C.  strongly  illuminant 
gases,  steam  and  tar  are  generated  while  the  coal  is  coked.  In 
the  second  period  (bright  red  glow)  the  coke,  decreasing  in 
volume,  yields  gases  (about  one-third  of  the  total  gas  volume) 
which  are  free  of  tar  and  of  low  illuminating  power.  The  coke 
remaining  at  the  end  of  the  first  period  is  probably  a  mixture  of 
very  stable  carbon-compounds  having  the  average  composition 
C16H40.  This  substance  is  further  decomposed  in  the  second 
period  at  high  temperature.  But  even  at  the  highest  practical 
heat  it  is  impossible  to  remove  the  traces  of  oxygen,  hydrogen 
and  nitrogen. 

If  large  quantities  of  coal  are  put  into  highly  heated  retorts, 
both  processes  take  place  simultaneously.  The  two,  however 
(coal  decomposition  and  coke  decomposition),  could  be  separated 
by  using  two  furnaces,  one  for  heating  the  material  to  600  degrees 
and  removing  the  tar,  the  other  to  decompose  the  coke.  Such 
a  separation  might  be  practicable  under  certain  conditions. 
The  experiments  made  by  Mueller  on  a  small  scale  confirm  the 
well-known  fact  that  only  one-fifth  of  the  nitrogen  of  the  coal 
is  present  in  the  form  of  ammonia  compounds ;  further,  that  the 
ammonia  is  formed  in  the  first  part  of  the  decomposition  of 
coke.  The  ammonia  yield  was 


Test. 

In  the  First  Period. 

In  the  Second  Period. 

No.  1 

0.065 

0.267 

2 

0.059 

0.144 

3 

0.108 

0.145 

4 

0.120 

0.178 

5 

0.063 

0.183 

6 

0.056 

0.242 

Average  

0.0785 

0.1931 

PEAT-COAL,   COKE  AND   BRIQUETTES 


219 


How  the  composition  of  the  products  changes  by  using  dif- 
ferent qualities  of  gas-coal  is  shown  in  Table  XCIV. 

TABLE   XCIV. 

CHANGE    IN    COMPOSITION    OF    PRODUCTS   WITH    QUALITY    OF    COAL. 


Bituminous  Coal  from 

Pas  de 

Calais. 

Eng- 
land. 

Comen- 
try. 

Blanzy. 

1 

H2O,  hygroscopic  
Ash 

2.17 
9.04 

2.70 
7.06 

3.31 
7.21 

4.34 
8.8 

6.17 
10.73 

•fl 

a. 

o              

5.56 

6.66 

7  71 

10.10 

11  70 

1  - 

H 

5  06 

5  36 

5  40 

5  53 

5  64 

§ 

C 

88  38 

86  97 

85  89 

83  37 

81  66 

0 

N  

1 

1 

1 

1 

1 

02            _ 
*    h    £ 

Gas  
Tar 

13.70 
3.90 

15.08 
4.65 

15.81 
5  08 

16.95 
5  48 

17 
5  59 

-§nT 

Ammonia  water  

4.59 

5.57 

6.80 

8.61 

9  86 

$2:* 

Coke 

71.48 

57  63 

64  90 

60  88 

58 

£°- 

Coal  dust  

6.33 

7.07 

7.41 

8.08 

9.36 

"5 

Volume,  cu.m  
Illuminating  power,  Carcell  .... 

30.13 
131c 

31.01 
112c 

30.64 
104c 

29.73 
102.  Ic 

27.44 
101.  8c 

^£3 

'o 

CO... 

CO                 

1.47 
6.68 

1.58 
7.17 

1.72 
8  21 

2.79 
9  86 

3.13 
11  93 

> 

H9 

54.21 

52.79 

50  10 

45  45 

42  26 

9 

CH4  

34.37 

34.43 

35.03 

36.42 

37  14 

c 

CH 

0  79 

0  99 

0  96 

1  04 

0  88 

CH  

2  48 

3  02 

3  98 

4  44 

4  76 

The  influence  of  the  mineral  substances  on  the  course  of  dis- 
tillation is  remarkable,  as  is  seen  from  Knoblauch's  researches. 
He  mixed  with  his  coal  2.5,  5,  and  10  per  cent  of  lime,  and  5  per 
cent  silica  respectively.  The  table  on  following  page  shows  the 
differences  of  yield  with  these  mixtures  (from  1000  kg?  of  coal). 

We  see  that  the  quantity  of  products  of  distillation  is  not 
changing  in  proportion  to  the  quantity  of  the  addition.  The 
gas  yield,  however,  seems  to  be  an  exception,  as  it  increases  in 
proportion  to  the  addition.  The  yield  in  ammonia  increases 
very  slowly  as  the  lime  is  added,  so  that  with  a  certain  quantity 
of  lime  a  maximum  is  reached,  above  which  even  a  large  addition 
of  lime  has  no  effect.  There  is  no  relation  between  silica  and 
ammonia  and  H2S,  since  no  reaction  takes  place.  The  small 
differences  shown  in  the  above  table  are  caused  by  variations  in 


220 


HEAT  ENERGY  AND  FUELS 


the  decomposition  of  the  coal,  since  the  quantity  of  coke 
increases  with  additions  more  rapidly  than  the  quantity  of  tar 
decreases,  and  since  at  the  same  time  gas  quantity  increases  the 
carbon  content  and  therefore  the  illuminating  power  of  the  gas 
is  necessarily  decreased,  which  decrease  is  not  sufficiently 
counterbalanced  by  the  increased  yield  of  gas. 

TABLE   XCV. 
EFFECT  OF  ADMIXTURE  OF  LIME  AND  SILICA  IN  DISTILLATION  PRODUCTS. 


1000  Kg.  Coal. 

Addition  of  Lime. 

Addition 
of 
Silica, 
5 
Per  cent. 

2.5 
Per  cent. 

5 
Per  cent. 

10 
Per  cent. 

Gas   cu   rn   incr68.se 

14.7 
16.8 
5.2 
0.483 
2.02 
1.42 
0.93 
21.3 
59.7 

20.1 
18.2 
7.9 
0.608 
2.53 
1.58 
1.03 
26.7 
66.2 

35.3 
17.5 
9.0 
0.929 
3.88 
1.81 
1.19 
40.9 
76.2 

21.5 

27.4 
11.8 
0.15 
0.67 
0.21 
0.138 
0.7 
8.8 

Coke    kg    increase 

Tar   kg.  decrease  . 

Ammonia,  kg.  increase  
Sulphate,  kg.  increase  
H2S   kg  decrease 

H2S,  cu.  m.,  decrease  
Ammonia   )  in  per  cent  (  increase 
H2S  J  of  yield        (  decrease 

For  coals  of  approximately  the  same  composition  as  the  test- 
coal  we  can  estimate  the  effect  of  adding  2.5  per  cent  of  lime  as 
follows : 

1.  The  yield  of  gas  is  increased  5  per  cent,  the  illuminating 
power  decreased  5  per  cent. 

2.  The  yield  of  coke  is  4  per  cent  higher,  of  which  2.5  per  cent 
is  lime,  so  that  the  actual  increase  of  coke-output  is  1.5  per  cent. 
This  increase  is  not  accompanied  by  an  increase  in  thermal 
value,  on  account  of  the  higher  ash  content. 

3.  The  quantity  of  tar  is  decreased  10  per  cent  and  its  quality 
deteriorated. 

4.  The  ammonia  output  is  increased  20  per  cent. 

5.  The  H2S  output  is  decreased  at  the  rate  of  1.4  per  1000  kg. 
coal. 

6.  The  C02  of  the  crude  gas  is  increased  10  per  cent. 

7.  The  formation  of  cyan  is  somewhat  decreased,  but  the 
quantity  of  ferrocyan  is  not  changed. 


PEAT-COAL,  COKE  AND  BRIQUETTES 


221 


This  point,  however,  and  also  the  question  as  to  what  extent 
the  higher  sulphur  content  of  the  coke  (in  the  above  case  about 
0.2  per  cent)  appears  as  combustible  sulphur,  have  to  be  further 
considered. 

W.  Jicinski  made  experiments  with  Moravian  (Austria)  coal 
from  Ostrau  of  5  mines ;  the  composition  is  given  in  Table  XCV, 
and  the  yield  from  destructive  distillation  is  given  in  Table  XCVI. 


TABLE  XCV. 

COMPOSITION  OF  MORAVIAN  COALS.  (Jicinski.) 


Percentage  of 

Air-dried 

Coking 

Coal  from 

Quality. 

C 

H 

0 

N 

Ash. 

Johann  .... 

81.74 

5.53 

6.18 

1.31 

5.24 

Good 

Gas  coal 

Adolf 

81  80 

5  23 

8  31 

1  76 

2  89 

Very  good 

Gas  coal 

Giinther  .  .  . 
Franziska.. 
Juliana..  .  . 

80.54 
83.35 
86.76 

5.09 
4.66 
4.06 

7.66 
5.06 
3.51 

1.43 
1.52 
1.30 

5.27 
5.37 
4.73 

Very  good 
Excellent 
Fair 

Coking  coal 
Coking  coal 
Anthracite  coal 

S  Content  :  0  .  50  to  1  .  05  per  cent.     P  Content  :  0  .  004  to  0  .  108  per  cent. 

TABLE  XCVI. 

YIELD    FROM   DESTRUCTIVE    DISTILLATION    OF   COALS   GIVEN   IN   TABLE 

XCV. 


Mine. 

Per  1  Kg.  of  Coal 
Cu.  M.  of  Gas. 

Coke  Residuum. 
Per  Cent. 

Johann  

30.86 

67.00 

Adolf  

30.02 

76.00 

Giinther  .  .  

29.96 

75.00 

Franziska  

28.60 

81.38 

Juliana  

27.12 

86.62 

The  ammonia  output  is  not  in  proportion  to  the  nitrogen 
content  of  the  coal.  Ammonia  seems  to  separate  from  some 
coals  easier  than  from  others.  As  an  average  about  0.75  of  the 
total  nitrogen  of  the  coal  remains  in  the  coke;  this  is  the  so-called 


22< 


HEAT   ENERGY  AND  FUE1LS 


coal-nitrogen,  which  is  only  gasified  by  the  complete  combustion 
of  the  coal.  About  0.25  of  the  total  nitrogen  —  the  ammonia 
nitrogen  —  takes  part  in  the  formation  of  ammonia.  But  even 
from  this,  one  part  escapes  as  cyan  or  as  free  nitrogen,  so  that 
the  quantity  of  nitrogen  actually  available  for  the  ammonia 
formation  is  only  0.188  to  0.089  of  the  total  nitrogen.  The  table 
below  shows  the  available  quantity  of  ammonia  nitrogen  in  some 
coals. 
The  tar  from  coke  ovens  contains  generally 

Benzene 0.9  -1.06  per  cent, 

Naphthalene 4.26-5.27  per  cent, 

Anthracen 0.57-0.64  per  cent, 

Pitch. 50  per  cent, 

Other  residuum 40  per  cent. 


TABLE   XCVII. 
AVAILABLE   QUANTITY  OF  AMMONIA  IN  COALS. 


Mine. 

rotal  N  in  Per 
Cent  of  Air- 
Dry  Coal. 

Available 
for  NH3. 

«! 

c  ^ 

ll 

£  •§, 

Available  Tar 
in  Per  Cent. 

6* 

o3 

$•8-; 

P-t    +a     « 

S|« 

m* 

rfl 

*d 

13 

v%  • 

Kaiserstul: 
Pluto 
Wilhelmin 
Johann 
Adolf 
Giinther 
Franziska 
Juliana 
Upper  Sile 
Friedenshc 
Karl,  Ge 
und  Vik 
England,  a 

ill 
[         Westphalia 
ej 

Austria 
sia,  average  

1.39 
1.45 
.77 
.31 
.76 
.43 
.52 
.30 
2.49 

Un- 
known 

1.40 

0.144 
0.146 
0.142 
0.140 
0.126 
0.120 
0.089 
0.134 
0.188 

Un- 
known 

0.167 

0.200 
0.212 
0.252 
0.184 
0.222 
0.172 
0.135 
0.175 
0.296 
0.168 

0.148 
0.235 

0.244 
0.258 
0.306 
0.244 
0.270 
0.210 
0.165 
0.213 
0.360 
0.204 

0.180 
0.286 

0.94 
1.00 
1.18 
0.94 
1.04 
0.81 
0.64 
0.82 
1.40 
0.79 

1.69 
1.11 

)» 

1.7 
1.7 
1.3 
2.6 
1.8 
3.6 
3.0 

2.5 
3.12 

>ffnung] 
org       [Lower  Silesia 
tor        J 
verage  

The  average  tar  output  on  a  large  scale  is  from  2  to  3  per  cent 
of  the  coal.  The  difference  between  coke  oven  gas  and  gas 
house  gas  is  given  in  Table  XCVIII. 


PEAT-COAL,  COKE  AND  BRIQUETTES 


223 


TABLE   XCVIII. 
ANALYSIS  OF  COKE  OVEN  AND  ILLUMINATING  GAS. 


Components. 

Coke  Oven 
Gas. 
Per  Cent. 

From  Gas 
House 
Per  Cent. 

Benzole  vapor  
Ethylene 

0.61 
1  63 

1.54 
*    1   19 

HS 

0.43 

CO, 

1  41 

0.87 

CO 

6  49 

5.40 

H2  
CH4  

53.32 
36.11 

55.00 
36.00 

Sum  

100.00 

100.00 

The  experiments  relative  to  the  yield  of  carbonizing  (coking) 
peat  made  by  Sir  Robert  Kane  and  Professor  Sullivan  have  given 
the  following  results : 


TABLE  XCIX. 

ANALYSIS  OF  COKE  OVEN  GAS. 


From  Alfre- 

From  an  Oven  at 

From 

ton  Coal, 

Seraing  (Ebelmen). 

Gas- 

Distilled 

Products  Obtained 
by  Coking 

forth 
Coal 

(Bunsen). 

2 

7| 

14 

Aver- 

(Bun- 

For- 

Back- 

Hours after  Starting. 

age. 

sen). 

ward. 

ward. 

Methane         

1   44 

1.66 

0.40 

1    17 

7  0 

6.6 

6.2 

Carbon  monoxide.  .  .  ..... 

4.17 

3.91 

2.19 

3.42 

1.1 

1.6 

6.3 

Carbon  dioxide  

10.13 

9.60 

13.06 

10.93 

1.1 

1.1 

2.3 

Olefine  gas  

0.7 

0.5 

1.6 

H2S  

0.5 

0.2 

0.2 

H 

6  28 

3  67 

1   10 

3  68 

0  5 

0  4 

1  4 

NH3  :... 

0.2 

0.2 

0.3 

N 

77  98 

81   16 

83  25 

80  80 

0  03 

HO 

7  5 

12  4 

Tar 

12  23 

9  7 

16.6 

Coke  

68.92 

67.2 

65.1 

Volatile  components  

30.8  to  32. 

7% 

Combustible  gases  

19.2  to  22.  3% 

100  pounds  of  peat  of  different  quality  was  coked  in  retorts 
similar  to  illuminating  gas  retorts.     The  volatile  matters  were 


224 


HEAT  ENERGY  AND  FUELS 


condensed  in  a  number  of  Woulf-bottles  and  in  a  cooled  coil. 
The  gases  were  also  collected  (Table  C). 


TABLE  C. 

PRODUCTS  OF  PEAT  DISTILLATION. 


Origin. 

Water. 

Tar. 

Coal. 

Gas. 

Even      mixture      of 

Light  peat 
Dense  peat 

light      and      heavy 
peat  of  Mount  Lu- 
cas Bog  near  Phil- 

23.600 

2.000 

37.500 

36.900 

lipstown. 

Light  peat 

from  Wood  of  Allen  .... 

32.273 

3.577 

39.132 

25.018 

Heavy  peat  from  Wood  of  Allen  .  .  . 

38.102 

2.767 

32.642 

26.489 

Upper  layer  of  Ticknevin  

38.628 

2.916 

31.110 

32.346 

Upper  layer  of  Ticknevin,  distilled 

at  red  glow  

32.098 

2.344 

23.437 

42.121 

Upper  layer  of  Shannon  

38.127 

4.417 

21.873 

35.693 

Dense  peat  

21.189 

1.462 

18.973 

57.746 

Averag 

e 

31.378 

2.787 

29.222 

36.606 

TABLE  CI. 
PRODUCTS  FROM  DISTILLATION  OF  PEAT. 


Origin. 

Tar  Water. 

Tar. 

Ammonia. 

Acetic  Acid 

_. 

"o 

5} 

cT 

0 

1 

d 

0 

*j 

h 

w« 

cf 

a  dJ 

^ 

S 

_o  nd 

* 

B 

fc 

&f 

d1 

|a 

1 

1 

3 

Even   mix- 

tures      of 

Light 

light     and 

peat 

heavy  peat 

0.302 

1.171 

0.076 

0.111 

0.092 

0.024 

0.684 

0.469 

Dense 

of     Mount 

peat 

Lucas  Bog, 
near  Phil- 

lipstown 

Light 

peat      from 

Wood  of  Allen  .  .  . 

0.187 

0.725 

0.206 

0.302 

0.171 

0.179 

0.721 

0.760 

Heavy 

peat     from 

Wood 

of  Allen  .... 

0.393 

1.524 

0.286 

0.419 

0.197 

0.075 

0.571 

q.565 

Upper  layer  of  Tick- 

nevin 

0.210 

0.814 

0.196 

0.287 

0.147 

0.170 

0.262 

0.617 

Upper  layer  of  Tick- 

nevin 

,  distilled  at 

red  glow  

0.195 

0.756 

0.208 

0.305 

0.161 

0.196 

0.816 

0.493 

Upper  layer  of  Shan- 

non 

0.404 

1.576 

0.205 

0.299 

0.132 

0.181 

0.829 

0.680 

Dense  p 

>eat 

0.181 

0.702 

0.161 

0.236 

0.119 

0.112 

0.647 

0.266 

Average  

0.268 

1.037 

0.191 

0.280 

0.146 

0.134 

0.790 

0.550 

PEAT-COAL,  COKE  AND  BRIQUETTES 


225 


The  analysis  of  the  tar  water  and  tar  showed  for  the  qualities 
given  in  Table  CI. 

Table  CII  gives  the  results  of  another  series  of  experiments  in 
which  a  part  of  the  peat  was  burned  by  means  of  a  blower. 


TABLE  CII. 

PEAT  DISTILLATION. 


Origin. 

Water. 

Tar. 

Ash. 

Gases. 

Light  peat  from  Wood  of  Allen  .... 
Heavy  peat  from  Wood  of  Allen  .  .  . 
Upper  layer  of  Shannon 

30.678 
30.663 
29  818 

2.510 
2.395 
2  270 

2.493 
7.226 
2  871 

63.319 
59.716 
65  041 

For  further  comparison  the  figures  given  in  Table  CIII,  taken 
from  both  series  of  experiments,  will  be  interesting : 


TABLE  CIII. 

PEAT  DISTILLATION. 


Origin. 

Tar  Water. 

Tar. 

NH3. 

Acetic 
Acid. 

Alcohol 
CH40 

Paraf- 
fin. 

Oil. 

Light  peat  from  Wood  of  Allen  
Heavy  peat  from  Wood  of  Allen  
Upper  layer  of  Shannon  

Average  

0.322 
0.344 
0.194 

0.179 
0.268 
0.174 

0.158 
0.156 
0.106 

0.169 
0.086 
0.119 

1.220 
0.946 
1.012 

0.287 

0.207 

0.140 

0.125 

1.059 

These  tables  also  give  an  idea  of  the  valuable  products  obtained 
by  distilling  peat.  Table  CIV  from  Muspratt's  Chemistry  gives 
the  yields  from  Irish  peat. 

TABLE  CIV. 

DESTRUCTIVE  DISTILLATION   OF  PEAT. 


Products  of  Destructive 

In  Closed 

With  Admission 

Distillation. 

Vessels. 

of  Air. 

Ammonia  

0.268 

0.287 

or  sulphate  of  ammonia 

1.037 

1.110 

Acetic  acid  

0.192 

0.207 

or  acetate  of  lime  

0.280 

0.305 

Wood  alcohol  

0.146 

0.140 

Oils  

1.340 

1.059 

Paraffin  

0.134 

0.125 

226 


HEAT  ENERGY  AND  FUELS 


TABLE  CV. 

DESTRUCTIVE  DISTILLATION   OF  PEAT. 


Yield  in  Per  Cent. 

Kane 
and 
Sullivan, 
Per  Cent. 

Hodges, 
Per  Cent. 

Prospectus 
of  Irish 
Peat  Company, 
Per  Cent. 

Sulphate  of  ammonia  

1.110 

1.000 

1   000 

Acetic  acid  
or  acetate  of  lime  
Wood  alcohol 

0.207 
0.305 
0  140 

0.328 
0  232 

0^700 
0  185 

Tar                           -               

2  390 

4  440 

Paraffin  
Oils  

0.125 
1.059 

0.104 

0.701 

The  average  composition  of  perfectly  dry  peat-coal  is 

C 75  to  85  per  cent 

H2 2  to  4    per  cent 

0 , 10  to  15  per  cent 

Ash 5  to  10  per  cent. 

The  per  cent  of  ash  can  be  as  high  or  higher  than  60  per  cent. 
Air-dry  peat-coal  contains  at  least  10  per  cent  of  hygroscopic 
water.  The  sulphur  and  phosphorus  content  of  the  ash  is  some- 
times considerable. 

TABLE  CVI. 
DESTRUCTIVE  DISTILLATION  OF  PEAT. 


Products  of  Distillation. 

Peat  from  Neumarkt 
(Wagenmann.) 

Peat  from 
Oldenburg, 
(Vohl). 

A. 

T> 

Per  Cent. 

Water  in  peat  
Ash  in  peat  

33.58 
6.76 

36.26 
5.49 

air  dry 

Coke 
Amn 
Amn 

Tar 

Gase 
Vapc 

T 

lonia  water  

27.70 
50.01 
0.32 
0.435 
1.103 
1.943 

K105 
0.304. 

|  17.400 

» 

-^ 

25.77 
58.03 
0.25 
0.380^ 
1.124 
2.389 

o'ees 

0.634. 
jll.ll 

0 
O5 

10 

35.3120 
40.0000 

1.7633* 
1.7715 

1  .  5582 
0.3005 
3.6695 

15.6250 

CO 
CO 
0 

O» 

lonia  in  same  
li^ht  oil  

heavy  oil  
paraffin  matter  ,  

asphalt 

paraffin  
creosote  
carbonaceous  residuum  
loss  
s  
>rs  

otal  

100.32 

100.10 

100.0000 

*  This  tar-output  is,  according  to  Stohmann,  entirely  too  high,  probably  on 
account  of  some  water  being  present. 


PEAT-COAL,   COKE  AND   BRIQUETTES  227 

Peat-coal  is  very  porous  and  light,  has  a  specific  gravity  of 
0.23  to  0.38,  absorbs  dyes  and  odoriferous  substances,  and  is 
therefore  used  for  removing  fusel  oil  from  brandy,  as  disinfectant, 
and  as  fertilizer. 

It  is  easily  ignited  and  continues  to  burn  even  with  very  weak 
draught.  The  calorific  value  varies  from  6500  to  7000  cal. 

Brown  coal  (lignite)  coke.  Earthy  brown  coal  disintegrates  in 
the  heat  and  therefore  cannot  be  coked.  Of  this  class  of  fuels 
lignite  and  pitch  coal  are  almost  the  only  ones  that  can  be  used 
for  this  purpose,  and  lignite  furnishes  a  coke  similar  to  charcoal. 
The  destructive  distillation  of  lignite  yields 

40  to  50  per  cent Coke 

12  to  20  per  cent Tar  water 

14  to  35  per  cent Tar 

12  to  25  per  cent Gases. 

Coke  from  bituminous  coal  is  generally  dark  gray,  sometimes 
silver  gray,  light  gray  or  black.  The  light  coke  is  melted,  the 
dark  generally  baked. 

Coke-oven  coke  is  generally  less  dense  than  gas-retort  coke, 
which  explains  the  advantage  of  the  former  in  metallurgical 
operations  and  firing.  According  to  Muck  the  specific  gravity 
varies  from  1.2  to  1.9. 

In  practice  the  strength,  and  composition  of  the  coke  is  of 
importance,  the  former  for  blast  furnaces  on  account  of  the  great 
weight  of  the  charge,  the  latter  on  account  of  deleterious  effects 
of  certain  substances. 

Director  Jugnet  has  found  the  following  data  relating  to 
strength  of  coke: 

Carve's  oven  70  cm 66.4    kg.  per  sq.  cm. 

Carve's  oven  66  cm 79.72  kg.  per  sq.  cm. 

Carve's  oven  50  cm 92.32  kg.  per  sq.  cm. 

Beehive  oven  50  cm 43.92  kg.  per  sq.  cm. 

Smet  oven      50  cm 42.12  kg.  per  sq.  cm. 

Coppee  oven  50  cm '.' .  . .  80.50  kg.  per  sq.  cm. 

Relative  to  the  composition,  the  quantity  of  sulphur  and 
phosphor  is  of  technical  importance. 

Coke  is  hard  to  ignite,  burns  with  a  short,  blue  flame,  and 


228  HEAT  ENERGY  AND  FUELS 

requires  a  strong  air  draught.     The  calorific  value  is  from  7000 
to  7800  cal. 

A  hair-like  formation,  called  coke-hair,  is  sometimes  formed 
on  the  surface  of  the  coke.  This  coke-hair  is  free  of  ash  and  is 
the  coked  residuum  of  tarry  products  of  distillation.  The 
composition  (dried  at  110°  C.),  according  to  V.  Platz,  is 

C 95.729  per  cent 

H2 0.384  per  cent 

O 3.887  per  cent 

Ash 

100.000  per  cent 

We  will  now  discuss  in  a  few  words  pressed  coal,  or  briquettes. 
In  order  to  utilize  the  culm  coal  it  has  been  attempted  (with  or 
without  suitable  binding  materials)  to  combine  the  small  pieces 
into  larger  pieces  called  briquettes,  and  we  have : 

Peat  briquettes  or  pressed  peat,  which  is  made  and  used  in  the 
vicinity  of  peat  deposits. 

Soft  coal  briquettes,  in  which  tar,  pitch,  asphalt,  starch, 
molasses,  clay,  gypsum,  alum,  lime  or  soluble  glass,  etc.,  is  used 
as  binder.  The  coal  dust  is  mixed  with  the  binder  and  pressed 
into  bricks.  They  have  frequently  the  disadvantage  of  develop- 
ing smoke  of  disagreeable  odor  or  containing  too  much  ash. 

Charcoal  or  coke  briquettes  are  made  in  the  same  way. 

Lignite  briquettes.  Here  the  resinous  and  other  organic 
matters  of  the  coal  serve  as  a  binder.  The  coals  are  dried  until 
they  contain  about  15  per  cent  of  water  and  are  then  pressed  hot 
(at  1000-1500  atm.  pressure).  The  content  of  water  is  necessary 
for  preventing  the  decomposition  of  the  organic  substances. 
The  manufacture  of  such  lignite  is  steadily  increasing  in  Germany 
and  Austria.  In  1901  120,000  carloads  of  briquettes  were  sold 
for  domestic  use  in  Berlin,  and  only  5000  carloads  of  soft  coal. 

The  combustion  of  these  briquettes  is  peculiar,  as  for  a  good 
utilization  of  the  fuel  a  very  weak  draught  has  to  be  used,  where- 
by the  lignite  is  burned  very  slowly,  giving  most  of  its  heat  off 
to  the  stove.  With  a  strong  draught  the  briquettes  are  burned 
quickly,  and  the  largest  part  of  the  heat  is  lost  through  the 
chimney. 

The  analysis  given  in  Table  CVII  is  taken  from  the  Zeitschrift 
des  Vereines  deutscher  Ingenieure  (1887,  page  91). 


PEAT-COAL,  COKE  AND  BRIQUETTES 


229 


TABLE  CVII. 
COMPOSITION  OF  LIGNITE  BRIQUETTES. 


Ash 

Water 

Volatile  matter. 
Fixed  carbon.  .  . 
Calorific  value.  . 


5.83 
19.81 

24.53  (74  Q 
48.83f74'3 
3203  Cal. 


5.59 

18.67 

24.93 

50.79 

3215  Cal. 


75.72 


5.93 

21.10 

28.52 

44.83 

3159  Cal. 


72.85 


5.95 

22.46 

16.74 

54.74 

2784  Cal 


71.48 


I  and  II  are  good,  III  and  IV  inferior  briquettes.     Briquettes 
from  Schallthal  (Styria)  contain: 

C 48.21  per  cent, 

H2 3.99  per  cent, 

0 19.92  per  cent, 

S 1.35  per  cent, 

H20  (hygroscopic) 15.63  per  cent, 

Ash 10.91  per  cent. 

Thermal  value 4280  cal. 

The  analysis  of  the  so-called  Clara  briquettes  shows : 

Elementary  analysis : 

C 48.72  per  cent, 

H2 5.80  per  cent, 

0  and  N 22.93  per  cent, 

Ash 12.62  per  cent, 

H20  (hygroscopic) 10.93  per  cent. 

Intermediate  analysis : 

H20  (hygroscopic) 10.93  per  cent, 

Volatile  matters 44.21  per  cent, 

Fixed  carbon.  . : 32.24  per  cent, 

Ash 12.62  per  cent. 

Calorific  value   (determined  in  calori- 
meter)    4656  cal. 

Effective  thermal  value   (H20  formed 

calculated  as  steam) 4349  cal. 

Calorific  value  of  the  coal  free  of  ash  and 

H20 5688  cal. 


CHAPTER  XVII. 
COKING   APPARATUS. 

THE  apparatus  for  manufacturing  coke  (and  peat-coal)  from 
raw  fuels  can  be  classified  as  follows: 

A.  Coking  in  piles. 

(a)  The  piles  are  built  with  coal  lumps  exclusively  and 
covered  with  earth.    The  pile  has  a  shaft  opening  in  the 
center  and  draught  holes  (Fig.  58). 
(ft)  The  pile  has  a  brick'  shaft  in  the  center  (Fig.  59). 
(7-)  A  channel  on  the  bottom  of  the  pile  and  a  movable  pis- 
ton in  the  shaft  serves  for  saving  the  products  of  distilla- 
tion: Dudley's  coke  pile. 


FIGS.  58  and  59.  —  Coke  Piles. 

B.  In  heaps. 

(a)  Analogous  to  the  heaps  used  for  charring  wood. 

(/?)  Heaps  temporarily  surrounded  with  boards  (like  Fou- 
cault's  charring  system).  The  heaps  are  made  either  rec- 
tangular or  circular. 

280 


COKING  APPARATUS, 


231 


C.  In  closed  piles  (kilns)  with  brick  walls  on  the  sides.  Gen- 
erally rectangular  and  provided  with  charging  doors  in  the  center 
of  both  short  sides.  Vertical  and  horizontal  air  channels,  which 


Charging  Door 


1  D 

D  1 

i  P 

Q  I 

•I  P 

P  l 

:  P 

n  1 

1  D 

n  i 

n     n               n     D 

FIGS.  60  and  61.  —  Closed  Piles  (for  coking). 


FIGS.  62  and  63.  —  Riesa  Oven. 


FIGS.  64  and  65.  —  Bee  Hive  Oven. 


can  be  partly  or  entirely  closed  with  bricks,  etc.,  transverse 
the  walls  and  serve  for  regulating  the  air  admitted.  The  pile 
is  covered  with  coke  culm  (Figs.  60  and  61).  The  Schaum- 
.  burger  coke  ovens  belong  to  this  class. 


232 


HEAT  ENERGY  AND  FUELS 


D.   Coking  in  closed  ovens. 

(a)  Ovens  with  admission  of  air  to  the  interior,  the  heat  for 
coking  being  furnished  by  partly  burning  the  coal  to  be 
coked.  To  this  class  belong  the  older  construction  of 
Riesa  (Figs.  62  and  63),  and  the  beehive  ovens  (Figs.  64 
and  65).  The  latter  are  largely  used  in  America  and 
England. 


FIG.  66.  —  Section  of  Francois-Rexroth  Coke  Oven. 


FIG  67.  —  Section  of  Francois-Rexroth  Coke  Oven. 

The  composition  of  the  gases  from  these  ovens  was  given  in  the 
last  chapter  (Table  XCIX).  Since  these  gases  contain  a  large 
amount  of  combustible  matter  at  a  high  temperature,  their  util- 
ization for  heating  purposes  was  suggested.  This  purpose  is 
frequently  accomplished  (in  connection  with  the  beehive  type) 
by  heating  boilers  with  the  gases;  in  this  case  the  boilers  are 


COKING   APPARATUS 


233 


built  on  top  of  the  oven, 
this  heat  are : 


Some  of  the  other  methods  of  utilizing 


(6)  Coke  ovens  without  admission  of  air  to  the  interior, 
which  are  heated   by  the   gases   generated   during  the 
coking  process.     The  coking  is  performed  in  chambers 
of  prismatic  form,  which  are  classified  as 
(a)  Horizontal  ovens: 

1.  Without  condensing  plant  for  the  gas. 

2.  With  condensing  plant  for  the  gas. 
(/?)  Vertical  ovens: 

1.  Without  condensing  plant  for  the  gas. 

2.  With  condensing  plant  for  the  gas. 

(f)  With  inclined  axis    (system  Powel  and  Dubo- 
chet)  has  not  come  into  practical  use. 


FIG.  68.  —  Coke  Oven,  System  Smet  (elevation). 


The  horizontal  ovens  are  constructed  in  different  styles  accord- 
ing to  the  path  of  the  gas  through  the  furnace.  The  most  im- 
portant types  are: 

Frangois-Rexroth  coke  oven  (Fig.  66  cross-section,  Fig.  67 
longitudinal  section  through  chamber). 


234 


HE  A  T   ENERGY  AND  FUELS 


FIG.  69.  —  Coke  Oven,  System  Smet  (plan). 


FIGS.  70  and  71.  —  Coke  Oven,  System  Smet  (details  of  doors). 
j,  ....235G... £....««?. ... 


FIG.  72.  • —  Coke  Oven,  Francois  (cross-section). 


COKIXG   APPARATUS 


235 


The  gases  leave  the  chambers  at  the  sides,  pass  through  two 
horizontal  channels  (in  the  side  walls)  then  through  two  horizon- 
tal channels  in  the  bottom  into  the  flue. 

Smet  coke  oven  (Fig.  68,  front  view  and  section;  Fig.  69, 
section  through  chambers  and  channels  in  the  bottom ;  Figs.  70, 
71,  details  of  doors). 

The  gases  go  as  in  the  previous  type  through  horizontal  chan- 


I 


!  ilLMMiffiJlli 


i-;  JjjWS  •,  ,,  ,,.  .;'«'^3 

FIG.  73.  —  Coke  Oven,  Francois  (longitudinal  section). 

nels  near  one  of  the  side-walls  and  under  the  floor  of  the  chamber. 
The  gases  leave  the  chamber  at  the  highest  point. 

Frangois  coke  oven  (Fig.  72,  cross-section ;  Fig.  73,  longitudinal 
section).  The  gases  of  distillation  leave  at  the  side,  the  same  as 
in  the  Frangois-Rexroth  system;  the  gases  are  carried  parallel  to 
the  wall  of  the  chamber  in  vertical  channels  downward,  under  the 
floor  of  the  chamber  (however,  in  horizontal  channels)  into  the 
flue. 

Similar  are  the  systems  of  Coppee  (Figs.  74,  75,  76,  77,  and  78), 
and  Dr.  Otto.  The  main  difference  between  these  and  the 
former  types  is  the  greater  height,  and  length  and  smaller  width 
of  the  chambers,  whereby  an  increase  in  the  heating  surface  is 
effected. 

Vertical  coke  ovens  without  condensation  belong  to  the  oldest 
types  (Appolt  system,  1854).  They  have  an  exceedingly  large 
heating  surface  and  were  at  one  time  held  in  high  esteem. 
They  are,  however,  very  much  more  expensive  to  build  and 


236 


HEAT  ENERGY  AND  FUELS 


FIGS.  74-78.  —  Copp6e's  Coke  Oven. 


COKING  APPARATUS  237 

operate  than  the  horizontal  ovens,  so  that  they  are  only  of 
historical  interest. 

In  the  destructive  distillation  of  coal,  besides  coke,  a  number 
of  by-products,  as  tar,  gas  water,  etc.,  are  obtained,  the  recovery 
of  which  in  many  cases  is  desirable  on  account  of  their  content  of 
valuable  substances  (ammonia,  benzol,  etc.),  notwithstanding  the 
loss  of  heat  by  cooling  and  the  decrease  in  calorific  value  by 
removal  of  the  products  of  condensation. 

As  the  by-product  recovery  in  the  coke  industry  is  coming 
more  and  more  into  use,  we  want  to  show  the  changes  in  oven 
construction  caused  by  the  introduction  of  this  process,  taking 
as  an  example  the  bottom-fire  oven  of  Dr.  Otto  (Figs.  79,  80,  81). 

The  gases  pass  up  through  two  pipes  provided  with  valves  and 
connected  to  the  highest  point  of  every  chamber  into  the  receivers 
a,  which  extend  across  the  entire  battery  of  ovens,  analogous  to 
the  hydraulic  main  in  a  gas  plant.  In  the  receiver  a  part  of  the 
tar  is  condensed,  and  the  gas  goes  through  condensing  and  puri- 
fying apparatus,  from  here  returning  to  the  ovens.  It  passes 
through  gas  pipes  b  (one  for  every  two  ovens)  to  the  burners  of 
the  combustion  chambers.  The  air  of  combustion  enters  around 
every  burner.  The  combustion  gases  go  through  the  center  of 
the  combustion  chamber  downward,  through  slots  into  a  side  flue 
(below  every  coking  chamber),  which  conducts  to  the  main  flue. 

In  the  more  modern  ovens  the  combustion  air  is  preheated  in 
regenerators  before  entering  the  ovens. 

The  coke  obtained  in  such  an  oven  is  removed  red  hot  and 
cooled  with  water,  for  preventing  combustion  in  the  atmosphere. 

For  making  peat-coal  (coke)  we  have,  besides  the  above 
apparatus, 

E.  Ovens  heated  exclusively  from  outside: 

(a)  With   a    special    fireplace    (Lottmann's    oven;    Crony 

retort  oven). 

(6)  With  superheated  steam  (Vignoles'  oven), 
(c)  With  combustion  gases  Crane's  oven,  using  solid  or 
gaseous  fuel. 

Finally  we  want  to  say  a  few  words  about  coking  of  lignite 
(brown coal),  which  is  carried  on  mainly  in  Saxony  and  Thuringia, 
where  coals  rich  in  paraffin  are  mined.  Rolle's  plate  oven  is 
almost  exclusively  used  for  this  purpose.  Such  an  oven  can  coke 


238 


HEAT  ENERGY  AND  FUELS 


COKIXG   APPARATUS 


239 


240  HEAT  ENERGY  AND  FUELS 

2500  kg.  of  lignite  in  24  hours,  with  a  coal  consumption  of  25  to 
30  per  cent  and  at  a  temperature  of  800  to  900°  C.    The  yield  is 

Tar 10  per  cent, 

Water 50  per  cent, 

Coke 32  per  cent. 

The  specific  gravity  of  the  tar  at  35°  C.  is  0.82-0.95. 

Suggestions  for  Lessons. 

Examination  of  different  artificial  solid  fuels;  elementary 
analysis,  calorific  value,  determination  of  the  ash,  sulphur  and 
phosphorus  content,  ash  analysis;  determination  of  specific 
gravity,  strength  and  porosity. 

Yield  by  destructive  distillation  of  carbonized  fuel,  gas,  tar 
and  tar  water,  also  ammonia,  acetic  acid,  etc.  Herein  the  influ- 
ence of  the  temperature  of  distillation,  slow  or  quick  heating,  of 
admixtures,  etc.,  has  to  be  studied. 


CHAPTER  XVIII. 


LIQUID    FUELS. 

To  this  class  belong  oil  (petroleum),  tar  from  destructive  dis- 
tillation of  coal  and  wood,  schist-oil,  and  to  a  small  extent  certain 
vegetable  oils,  alcohol,  turpentine,  benzine,  etc. 

The  liquid  fuels  have  the  advantage  of  burning  up  without 
residuum.  Such  a  residuum  as  remains  of  solid  fuels  might 
obstruct  the  grate,  cause  uneven  air  supply  and  incomplete  com- 
bustion. 

The  utilization  however,  of  liquid  fuels  presents  some  serious 
difficulties  and  makes  the  construction  of  well  designed'  and 
carefully  tested  burners  imperative.  The  main  difficulty  is  the 
atomization,  otherwise  carbon  is  deposited,  which  will  cause 
stoppages  and  block  the  flow  of  the  liquid. 

A  general  use  of  liquid  fuel  is  prevented  by  high  cost.  How- 
ever, under  certain  local  conditions  it  can  be  used  economically. 

The  experiments  for  introducing  alcohol  as  fuel  on  a  large  scale 
have  so  far  not  been  successful. 

Table  CVIII  contains  some  data  relating  to  the  use  of  liquid 
fuels. 

TABLE  CVIII. 

COMPOSITION  OF  LIQUID   FUELS. 


Kind  of  Fuel. 

Composition  in  Per  cent. 

Calorific 
Value  in 
Kg-cal. 

C. 

H. 

o. 

Ash. 

American  crud.6  oil 

83.0 
85.0 
85.5 
90.0 
87.0 
86.7 

14.0 
11.5 
14.2 
5.0 
13.0 
13.0 

3.0 
3.5 
0.3 
5.0 

0.3 

11100 
10300 
11046 
8900 
10900 
10805 
8830 
8830 
9620 

Caucasian  crud.6  oil 

Refined  American  oil  
Coal  tar  
Heavy  oil  from  American  petroleum 
Heavy  oil  from  Caucasian  petroleum 
Schist  oil 

Tar  oil 

'77  '.2 

ii'7 

11.1 

Rape  oil  . 

241 


242 


HEAT  ENERGY  AXD  FUELS 


The  source  of  oxygen  in  petroleum  is  dissolved  water;  in  coal 
tar  the  oxygen  is  partly  chemically  combined,  partly  from  water. 


TABLE  CIX. 
COMPOSITION  OF  LIQUID   FUELS. 


Liquid  Fuel. 

Burnt  to 

Calorific 
Kg-ca 

Value  in 

1.   I  XT 

1  Kg. 

1  Mol. 

Benzole  
Hexane  •  
Hexane  

CO2  and  H2O  liquid 
'       '               vapor 

9997 
11525 
10636 

779800 
991200 
914800 

Heptane  
Alcohol 

liquid 

11375 
7054 

1137500 
324500 

Glycerine  
Butter  
Animal  fat  average  ...... 

lit                                     iC 

4316 
9231 
9500 

397100 

The  residuum  of  the  first  distillation  of  crude  oil  is  sold  in 
Russia  under  the  name  of  Masut.  When  heated  to  150  degrees 
it  generates  combustible  gases,  can  be  ignited  at  215  degrees, 
ignites  itself  at  300  degrees,  and  its  specific  gravity  is  0.91. 
The  calorific  value  is  11,000  cal.  In  practice  62  kg.  Masut 
replace  100  kg.  good  bituminous  coal.  1000  liters  of  air  are 
necessary  to  burn  1  kg.  Masut  completely. 

Table  CX  shows  comparative  data  (Wright)  which,  however, 
change  according  to  the  construction  of  the  fire-place. 


TABLE  CX. 
THERMAL  EFFICIENCY  OF  FUELS. 


Calculated 

Actual 

Thermal 

Evaporation, 

Evaporation, 

Efficiency, 

Lb.  English. 

Lb.  English. 

Per  Cent. 

Nottingham  cannel  coal  

12.27 

8.78 

71.56 

Gas  coal 

14  24 

10.01 

70.30 

Cannel  coal  

12.23 

9.91 

81.03 

Gas-house  coke  

13.83 

11.15 

80.62 

Tar  :  

15.06 

12.71 

84.40 

Creosote.  .  J  

16.78 

13.35 

79.56 

CHAPTER  XIX. 
GASEOUS    FUELS. 

THE  gaseous  fuels  have,  like  the  liquid  fuels,  the  advantages 
of  burning  up  without  residue,  of  easy  transportation  to  the 
place  of  combustion,  and  of  convenient  regulation  of  tempera- 
ture. Furthermore,  the  length  of  the  flame  can  be  varied  within 
certain  limits,  and  for  complete  combustion  a  considerably 
smaller  excess  of  air  is  required  than  with  solid  and  liquid  fuels. 
The  gaseous  fuels,  therefore,  have  a  higher  temperature  of  com- 
bustion, and  generate  a  smaller  quantity  of  gaseous  products  of 
combustion  than  other  fuels  of  the  same  composition,  whereby 
a  better  utilization  of  the  generated  heat  can  be  secured. 
Another  advantage  is  that  in  this  case  not  only  the  air  for  com- 
bustion but  also  the  gas  can  be  preheated. 

Such  gaseous  fuel  occurs  in  nature  and  is  then  called  natural 
gas.  The  average  composition  of  Pennsylvania  natural  gas  is 

Methane 67     per  cent, 

Hydrogen. . 22     per  cent, 

Nitrogen 3     per  cent, 

Ethane 5     per  cent, 

Ethylene 1     per  cent, 

Carbon  dioxide 0.6  per  cent, 

Carbon  monoxide 0.6  per  cent. 

As  the  occurrence  of  natural  gas  is  limited,  similar  gases  are 
artificially  produced  for  industrial  use  by  the  following  methods : 

1.  Dry  distillation  of  substances  containing  carbon,  as  coal, 
lignite,  peat,  wood,  fat,  etc.,  whereby  gases  of  distillation  (illu- 
minating gas)  are  obtained.     According  to  the  raw  material  used 
the  manufactured  gas  is  called  coal  gas,  peat  gas,  wood  gas,  fat 
gas,  oil  gas,  etc. 

2.  Incomplete  combustion  of  coal  with  insufficient  amount 
of  air,  whereby  generator  gas,  also  called  producer  gas  or  air  gas, 
is  obtained. 

243 


244  HEAT  ENERGY  AND  FUELS 

3.  Decomposition  of  water  (steam)  by  glowing  coal  or  com- 
bustion of  coal  by  means  of  steam,  whereby  water  gas  is  obtained. 

In  special  cases  other  methods  are  used  for  producing  fuel 
gases,  as  for  instance : 

4.  Incomplete  combustion  of  coal  by  simultaneous  action  of 
air  and  oxides,  the  latter  thereby  being  reduced.     This  reaction 
takes  place  in  iron  blast  furnaces  and  furnishes  a  gas  of  high 
fuel  value,  low  in  nitrogen  and  high  in  carbon  monoxide,  which 
is  called  blast-furnace  gas.     If  water  is  used  as  oxide,  semi-water 
gas  or  Dowson  gas  is  obtained. 

5.  For  getting  high  temperatures  or  high  luminant  power, 
acetylene  C2H2  is  sometimes  used,  which  is  obtained  by  reaction 
of  calcium  carbide  and  water: 

CaC2  +  2  H20  =  Ca  (OH)2  +  C2H2. 
We  therefore  have  the  following  summary  of  methods  for  the 

PRODUCTION  OF  FUEL  GASES. 

1.  By  dry  distillation : 
From  coal,  coal  gas, 
From  peat,  peat  gas, 
From  wood,  wood  gas, 
From  fat,  fat  gas, 
From  oil  residue,  oil  gas. 

2.  By  incomplete  combustion  of  coal : 

(a)  With  air  alone,  producer  gas  (air  gas). 
(6)  With  air  and  oxides  of  metals  Fe203,  etc.,  blast-furnace 
gas. 

(c)  Air  and  steam,  Dowson  gas. 

(d)  Air  and  carbon  dioxide,  regenerated  combustion  gases. 

3.  By  decomposing  carbides  with  water: 
Mainly  calcium  carbide,  acetylene. 

Leaving  aside  the  acetylene  and  the  blast-furnace  gas,  which 
are  only  of  local  importance,  the  following  industrial  gases  have 
to  be  mainly  considered: 

(1)  Gases  of  distillation,  obtained  by  dry  distillation  of  car- 
bonaceous substances. 

(a)  Illuminating  gas  made  in  retorts.     It  is  used  for  illum- 
inating, heating  and  for  internal  combustion  engines. 


GASEOUS  FUELS  245 

As  an  example,  the  composition  of  French  illuminating  gas 
is  given  below,  which  is  identical  all  over  France : 
Weight  of  cubic  meter  =  0.523  kg. 
Thermal  value  of  1  cubic  meter  =  5600  cal. 
Weight  of  22.42  liters  =  2  grams. 
Thermal  value  of  2  grams  =  125  cal. 


Analysis  in  per  cent  by  weight : 

Carbon,  43.2  per  cent, 

Hydrogen,  21.3  per  cent, 

Oxygen  and  nitrogen,  25.5  per  cent. 

Analysis  in  per  cent  by  volume : 

51.0  per  cent  H2 
33.0  per  cent  CH4 

8.8  per  cent  CO 

1.8  per  cent  CO2 

1.0  per  cent  02  +  N2 

1.1  per  cent  C6H6 

3.3  per  cent  absorbable  CnH2n 


100.0 

.(b)  Gases  of  distillation,  produced  as  by-product  in  the 
coking  or  charring  of  fuels,  mainly  coke-oven  gas. 

(2)  Generator  gas,  air  gas,  or  producer  gas  is  properly  the 
name  of  such  gas  only,  which  is  made  from  carbon  (charcoal  or 
coke) ;  i.e.,  from  a  coal  free  from  hydrogen  and  oxygen,  and  using 
dry  air  for  the  incomplete  combustion.     In  practice,  however, 
we  comprise  under  the  classification  " generator  gas"  any  gas 
generated  in  certain  apparatus  (gas  producers)  by  leading  air 
without  steam  through  a  glowing  layer  of  fuel  of  sufficient  height. 
The  air  never  being  dry,  we  get  in  practice  always  a  mixture  of 
generator  gas  and  water  gas,  and  also  gases  of  distillation  if 
crude,  uncoked  fuel  is  used. 

(3)  Water  gas  is  used  for  illuminating  and  fuel  purposes. 

(4)  Semi-water  gas  or  Dowson  gas  is  used  for  fuel  and  power 
purposes,  and  is  prepared  by  leading  a  mixture  of  air  and  steam 
through  a  coal  layer  in  a  producer. 


CHAPTER  XX. 
PRODUCER   GAS. 

IF  air  is  led  at  moderate  speed  through  a  layer  of  pure  carbon 
(in  practice  charcoal  or  coke),  incomplete  combustion  takes  place; 
i.e.  by  the  reaction  of  oxygen  on  the  glowing  coal,  formation  of 
carbon  monoxide  occurs : 

C  +  i  02  =  CO. 

Supposing  the  air  to  contain  4  mols  nitrogen  to  1  mol  oxygen, 
which  is  probably  correct,  we  can  write  the  reaction : 

C  +  }  02  +  2  N2  =  CO  +  2  N2, 

and  we  get  a  gas  which  theoretically  contains  2  mols  N2  to  1  mol 
CO,  and  should  have  the  composition : 

CO  33 . 3  per  cent  by  volume. 
N    66.7  per  cent  by  volume. 

This  gas  ought  to  yield  per  22.42  liters  if  burned  at  constant  vol- 
ume 0.333  X  67.9  =  22.61  cal.  If  burned  at  constant  pressure 
22.61  +  0.5  X  0.54  =  22.88  cal.  The  thermal  value  of  the  same 
at  constant  pressure  would  be  per  cubic  meter  1020.5  cal. 

The  thermal  value  of  1  gram  of  gas  is  calculated  as  follows: 
According  to  the  equation  the  gas  has  for  every  gram  atom  of 
carbon 

12  grams  carbon  j  2§  n  monoxide_ 

16  grams  oxygen  ) 
56  grams  nitrogen. 
Sum     84  grams. 

As  84  grams  of  gas  contain  3  mols  (CO  +  2  N2),  22.42  liters  of 
the  same  at  0°  C.  and  760  mm.  are  equal  to  28  grams,  and  there- 
fore 1  gram  of  gas  generates  817  cal. 

This  reaction,  however,  only  takes  place  at  very  high  tempera  - 

246 


PRODUCER  GAS  247 

tures.  At  lower  temperatures  a  second  reaction  occurs  simul- 
taneously, and  the  extent  to  which  it  occurs  increases  with 
decreasing  temperature.  This  reaction  is 

C  +  02  =  C02, 

/ 

or,  if  the  air  is  used  instead  of  oxygen, 

C  +  02  +  4  N2  =  C02  +  4  N2, 

Between  these  two  reactions  there  exists  a  certain  equilibrium 
for  every  temperature  and  pressure.  If  we  subtract  the  equation 

C     +    02  =     C02 

from  2  C     +    02  =  2  CO, 

we  get  2  CO  =  C02  +     0, 

which  reaction  actually  takes  place  at  fairly  high  temperatures, 
and  determines  the  proportion  of  the  two  first  reactions.  It  is 
reversible : 

2  CO  <±  C02  +  C. 

That  is,  while  pure  CO  within  certain  temperatures  is  decom- 
posed into  C02  and  C,  we  find  that  under  similar  conditions  CO  is 
produced  by  reduction  of  C02  by  means  of  C.  Therefore,  there 
exists  necessarily  an  equilibrium  between  CO,  C02  and  C,  which 
depends  on  the  temperature  and  concentration  (gas  pressure). 

Since  out  of  two  volumes  CO  only  one  volume  C02  is  formed, 
and  since  the  reaction,  according  to  our  equation  (from  left  to 
right),  takes  place  without  decrease  of  volume,  it  is  clear  that  an 
increase  of  pressure  facilitates  the  formation  of  C02,  while  a 
decrease  of  pressure  favors  the  formation  of  CO.  Therefore,  the 
primary  air  (wind)  in  a  gas  producer  should  be  of  low  pressure  if 
a  gas  high  in  CO  is  desired. 

The  influence  of  temperature  on  the  equilibrium  is  shown  by 
the  balance  of  the  reaction  heats : 

C  +  02  =  C02  +  97,600  cal. 
2  (C  +  0)  =  2  CO  +  57,800  cal. 
2  CO  =  C02  +  C  +  39,800  cal. 


248 


HEAT  ENERGY  AND  FUELS 


i.e.,  the  decomposition  of  2  CO  into  C02  and  C  takes  place  under 
generation  of  heat.  Therefore  an  increase  of  temperature  facili- 
tates the  formation,  a  decrease  of  temperature  the  decomposition 
of  CO.  Thence  it  is  clear  that  the  gas  will  be  the  richer  in  CO 
with  higher  temperature. 

All  these  observations  are  of  importance  for  the  state  of  equi- 
librium.   Whether  this  is  reached  in  practice  or  not  depends  on 


Vol.% 


Vol.% 


CO, 

^ 


10          I     ^^      1  I  I  I  I    ^f       1° 1    ^^       I 1 l^^kn.      I 1 

500      600        700        800        900       10CO      1100      12001300     500      600       700        800        900       1000      1100      1200    130C 


FIG.  82.  —  Ideal  Composition  of  Gener- 
ator  Gas  from  Pure  Oxygen. 


FIG.  83.  —  Ideal  Composition  of  Gener- 
ator Gas  from  Dry  Air. 


the  height  of  the  coal,  porosity  of  same,  velocity  of  wind,  etc.  It 
is,  however,  of  the  greatest  importance  for  the  theory  of  the  gas 
producers  as  well  as  for  the  practice,  to  know  the  equilibrium  for 
all  the  different  conditions,  since  the  only  way  to  judge  the 


PRODUCER  GAS 


249 


quality  of  a  gas  producer  process  is  to  compare  the  results 
obtained  in  practice  with  those  corresponding  to  the  theoretical 
equilibrium. 

We  therefore  give  in  Tables  CXI,  CXII,  and  CXIII  the  ideal 
composition  of  generator  gas  at  different  temperatures  and 
pressures. 

Table  CXI  gives  the  ideal  composition  of  producer  gas,  pro- 
duced with  pure  oxygen.  Fig.  82  shows  the  content  of  this  table 
graphically. 


TABLE  CXI. 

IDEAL   COMPOSITION    OF    PRODUCER  GAS  (GENERATOR  GAS)   PRODUCED 
WITH  PURE  OXYGEN. 


Air  Pressure. 

1  Atmosphere. 

2   Atmospheres. 

Volumetric  Composition 
at  a  Temperature  of 

CO 

C02 

CO 

C02 

227°  C.   .     500°  abs. 

0.004 

99.996 

0.0028 

99.9972 

327°             600° 

0.123 

99.877 

0.087 

99.913 

427°             700° 

1.427 

98.573 

1.011 

98.989 

527°             800° 

8.794 

91.206 

6.303 

93.697 

627°             900° 

32.542 

67.458 

24.809 

79.191 

727°           1000° 

70.35 

29.65 

58.105 

42.259 

827°           1100° 

92.75 

7.25 

87.198 

12.802 

927°           1200° 

98.445 

1.555 

97.00 

3.00 

1027°           1300° 

99.50 

0.50 

99.00 

1.00 

Air  Pressure. 

3   Atmospheres. 

4   Atmospheres. 

Volumetric  Composition 
at  a  Temperature  of 

CO 

CO_, 

CO 

C02 

227°  C.        500°  abs. 

0.0023 

99.9977 

0.002 

99.998 

327°            600° 

0.0711 

99.9289 

0.061 

99.939 

427°            700° 

0.826 

99.174 

0.716 

99.284 

527°             800° 

5.177 

94.823 

4.499 

95.591 

627°             900° 

20.408 

79.592 

17.945 

82.055 

727°           1000° 

51.788 

48.212 

47.017 

52.983 

827°           1100° 

-82.72 

17.28 

78.987 

21.013 

927°           1200° 

95.65 

4.35 

94.315 

5.685 

1027°           1300° 

98.97 

1.03 

98.67 

1.33 

Table  CXII  gives  the  ideal  composition  of  producer  gas,  pro- 
duced with  dry  atmospheric  air.  The  data  of  this  table  are 
graphically  shown  in  Fig.  83. 


250 


HEAT  EX ERG Y  AND  FUELS 


TABLE  CXII. 

IDEAL   COMPOSITION    OF   PRODUCER   GAS    (GENERATOR   GAS)    PRODUCED 
WITH  DRY  ATMOSPHERIC  AIR. 

Air  Pressure  =  1  Atmosphere. 


Partial 

Gasifying  Temperature. 

Pressure  of 

Composition  in  Per  Cent  by  Volume. 

CO+C02. 

°C. 

T°  abs. 

In  Atm. 

C02. 

CO. 

N2. 

227° 

500° 

0.21 

21.00 

79.00 

327° 

600° 

0.21 

21.00 

79.00 

427° 

700° 

0.2145 

20.31 

1.14 

78.55 

527° 

800° 

0.24 

16.40 

7.60 

76.00 

627° 

900° 

0.29 

8.75 

20.25 

71.00 

727° 

1000° 

0.334      ' 

2.14 

31.26 

66.60 

827° 

1100° 

0.344 

0.47 

33.93 

65.60 

927° 

1200° 

0.346 

0.14 

34.46 

65.40 

1027° 

1300° 

0.3465 

0.01 

34.65 

65.35 

Air  Pressure  =  2  Atmospheres. 

227° 

500° 

0.42 

21.00 

79.00 

327° 

600° 

0.42 

21.00 

79.00 

427° 

700° 

0.4228 

20.39x 

1.01 

78.60 

527° 

800° 

0.466 

18.14 

5.82 

76.70 

627° 

900° 

0.555 

11.94 

17.09 

72.25 

727° 

1000° 

0.6535 

4.31 

29.56 

67.32 

827° 

1100° 

0.6865 

0.83 

33.74 

65.67 

927° 

1200° 

0.692 

0.21 

34.44 

65.40 

1027° 

1300° 

0.693 

0.10 

34.56 

65.35 

Air  Pressure  =  3  Atmospheres. 

227° 

500° 

0.63 

21.00 

79.00 

327° 

600° 

0.63 

21.00 

79.00 

427° 

700° 

0.6395 

20.51 

0.81 

78.68 

527° 

800° 

0.686 

18.14 

4.76 

77.00 

627° 

900° 

0.8075 

11.94 

14.98 

73.08 

727° 

1000° 

0.957 

4.31 

27.59 

68.10 

827° 

1100° 

1.625 

0.83 

33.37 

65.80 

927° 

1200° 

1.0365 

0.21 

34.34 

65.45 

1027° 

1300° 

1.04 

0.10 

34.56 

65.34 

PRODUCER  GAS 


251 


TABLE  CXII.  —  Continued 
Air  Pressure  =  4  Atmospheres. 


Partial 

Gasifying  Temperature. 

Pressure  of 

Composition  in  Per  Cent  by  Volume. 

CO  +  C02. 

°C. 

T°  abs. 

In  Atm. 

C02. 

CO. 

N2. 

227° 

500° 

0.84 

21.00 

79.00 

327° 

600° 

0.84 

21.00 

79.00 

427° 

700° 

0.851 

20.59 

0.71 

78.70 

527° 

800° 

0.905 

18.52 

4.11 

77.37 

627° 

900° 

1.056 

12.73 

13.67 

73.60 

727° 

1000° 

1.258 

5.00 

26.46 

68.55 

827° 

1100° 

1.359 

1.13 

32.85 

66.02 

927° 

1200° 

1.381 

0.28 

34.25 

65.47 

1027° 

1300° 

1.385 

0.13 

34.50 

65.37 

TABLE  CXIII. 

IDEAL  COMPOSITION  OF  PRODUCER  GAS  (GENERATOR  GAS)   PRODUCED 
WITH   50   PER  CENT  OXYGEN. 

Air  Pressure  =  1  Atmosphere. 


Partial 

n 

Gasifying  Temperature. 

Pressure  of 

Composition  in  Per  Cent  by  Volume. 

CO+C02. 

•CL 

T°  abs. 

In  Atm. 

CO2. 

CO. 

N2. 

227° 

500° 

0.50 

50.00 

50.00 

327° 

600° 

0.50 

50.00 

50.00 

427° 

700° 

0.502 

49.40 

'0.80 

49.80 

527° 

800° 

0.522 

43.40 

8.80 

47.80 

627° 

900° 

0.568 

29.60 

27.20 

43.20 

727° 

1000° 

0.633 

10.10 

53.20 

36.70 

827° 

1100° 

0.66 

2.00 

64.00 

34.00 

927° 

1200° 

0.663 

1.10 

65.20 

33.70 

1027° 

1300° 

0.6655 

0.35 

66.20 

33.45 

Air  Pressure  =  2  Atmospheres. 

227° 

500° 

I. 

49.56 

50.00 

327° 

600° 

1. 

45.65 



50.00 

427° 

700° 

'  1.0035 

34.03 

6.61 

49.83 

527° 

800° 

1.0295 

15.50 

5.83 

48.52 

627° 

900° 

1.1065 

34.03 

21.30 

44.67 

727° 

1000° 

1.23 

15.50 

46.00 

38.50 

827° 

1100° 

1.308 

3.80 

61.60 

34.60 

927° 

1200° 

1.326 

1.10 

65.20 

33.70 

1027° 

1300° 

1  .  3305 

0.43 

66.10 

33.47 

252 


HEAT  ENERGY  AND  FUELS 


TABLE   CXIII.  —  Continued 
Air  Pressure  =  3  Atmospheres. 


Partial 

Gasifying  Temperature 

Pressure  of 

Composition  in  Per  Cent  by  Volume. 

CO  +  CO2. 

°C. 

T°  abs. 

In  Atm. 

C02. 

CO. 

N2. 

227° 

500° 

1.5 

50.00 

50.00 

327° 

600° 

1.5 

50.00 

50.00 

427° 

700° 

1  .  5045 

49.55 

0.60 

49.85 

527° 

800° 

1.538 

46.20 

5.07 

48  .  73 

627° 

900° 

1  .  6345 

36.55 

17.93 

45.52 

727° 

1000° 

1.814 

18.60 

41.87 

39.53 

827° 

1100° 

1.9455 

5.45 

59.40 

35.15 

927° 

1200° 

1.986 

1.40 

64.80 

33.80 

1027° 

1300° 

1  .  9955 

0.45 

66.07 

33.48 

Air  Pressure  =  4  Atmospheres. 

227° 

p 
500° 

2. 

50.00 

50.00 

327° 

600° 

2. 

50.00 

50.00 

427° 

700° 

2.0053 

49.60 

0.54 

49.86 

527° 

800° 

2.0443 

46.68 

4.43 

48.89 

627° 

900° 

2.1615 

37.89 

16.15 

45.96 

727° 

1000° 

2.384 

21.20 

38.40 

40.40 

827° 

1100° 

2.588 

5.90 

58.80 

35.30 

927° 

1200° 

2.6435 

1.74 

64.35 

33.91 

1027° 

1300° 

2.6605 

0.46 

66.05 

33.49 

Since  it  is  not  improbable  that  in  future  a  mixture  of  50  per 
cent  oxygen  and  50  per  cent  nitrogen  may  be  used  in  gas  pro- 
ducers, the  data  for  this  case  are  given  in  Table  CXIII.  Fig.  84 
gives  the  results  graphically. 

The  following  important  general  conclusions  may  be  drawn 
from  these  tables  and  diagrams : 

1.  In  all  cases  the  C02  content  of  the  ideal  generator  gas  at 
low  temperature  is  a  maximum,  which  is  practically  constant 
up  to  400°  C. 

2.  With  increasing  temperature  the  C02  content  is  decreasing; 
between  800°  and  1000°  C.  no  C02  is  present. 

3.  No  CO  is  found  up  to  about  400°  C. 

4.  With  increasing  temperature  the  CO  content  is  increasing 
and  is  reaching  a  maximum  at  800°  to  1000°  C. 

5.  At  constant  temperature  the  C02  content  is  increasing  with 


PRODUCER  GAS 


253 


the  pressure,  and  therefore  also  with  the  oxygen  content  of  the 
primary  air. 

6.  CO  shows  the  opposite  property. 

7.  At  low  temperatures  the  absolute  C02  content  is  increasing 
with  the  oxygen  content  of  the  primary  air. 

8.  At  high  temperatures  the  absolute  content  of  the  gas  in  CO 
is  increasing  with  the  oxygen  content  of  the  primary  air. 


Vol.% 


700        800       900       1000     1100      1200       1300 

FIG.  84.  —  Ideal  Composition  of  Generator  Gas  from  50  per  cent  Oxygen. 

Therefore  the  following  facts  have  to  be  considered  for  getting 
a  generator  gas  of  the  highest  possible  thermal  value  and  also  rich 
in  CO. 

1.  The  oxygen  content  of  the  primary  air  being  the  same,  the 
gasifying  temperature  has  to  be  high.     In  practice  a  temperature 
of  700°  to  900°  C.  is  sufficient,  as  at  this  temperature  the  maxi- 
mum CO  content  is  practically  reached. 

2.  At  high  gasifying  temperatures  the  quality  of  generator  gas, 
i.e.,  the  content  of  CO,  is  increasing  with  the  oxygen  content  of 
the  primary  air. 

3.  High  air  (wind)  pressures  are  unfavorable,  as  thereby,  under 
otherwise  constant  conditions,  the  C02  content  is  increased.     If, 


254  HEAT  ENERGY  AND  FUELS 

however,  it  is  desired  to  generate  the  largest  possible  quantity  of 
C02  in  the  producer,  which  is  sometimes  the  case  in  the  hot  blow- 
ing period  of  the  water-gas  process  for  the  purpose  of  rapidly 
increasing  the  temperature,  a  very  low  temperature  has  to  be 
kept  during  the  process  if  the  equilibrium  is  to  be  reached.  This 
is  easily  understood,  as  with  increasing  temperature  the  quantity 
of  the  CO  formed  is  rapidly  increasing,  and  the  quantity  of  C02 
is  decreasing.  If  in  the  producer  the  equilibrium  is  reached,  the 
temperature  of  the  producer  must  not  get  high  if  it  is  the  inten- 
tion to  get  a  high  yield  of  C02.  These  conditions  are  not  changed 
by  increasing  the  oxygen  content  of  the  primary  air. 

From  the  above  facts  we  can  calculate  the  volume  proportions 
of  C02  to  CO,  of  C02  to  CO  +  C02  and  of  CO  to  CO  +  C02,  also 
the  quantity  of  carbon  gasified  by  a  certain  volume  of  air,  the 
quantity  of  air  necessary  for  gasifying  a  certain  quantity  of  car- 
bon, and  also  the  quantity  of  carbon  and  air  required  for 
generating  a  certain  volume  of  ideal  generator  gas. 

We  have  so  far  treated  the  ideal  generator  gas,  i.e.,  a  gas  which 
is  produced  by  the  action  of  dry  primary  air  on  glowing  coal, 
under  the  supposition  that  in  the  process  of  combustion  the  state 
of  equilibrium  is  reached. 

We  now  have  to  consider  the  case  in  which  equilibrium  is 
not  reached,  this  case  occurring  very  frequently  in  practice. 

Every  single  layer  of  coke  consists  of  pieces  of  coke  and  air 
spaces  between.  The  larger  the  pieces  of  coke  the  larger  the  air 
spaces.  With  coke  of  fist  size,  the  air  spaces  amount  to  one- 
quarter  to  one-fifth  of  the  total  volume,  and  these  spaces  allow  the 
air  to  pass  through  the  producer. 

Every  piece  of  coal,  therefore,  is  surrounded  by  a  layer  of  air 
varying  in  thickness  from  a  few  millimeters  to  a  few  centimeters. 
The  reaction  between  the  oxygen  of  the  air  and  the  coal  takes 
place  only  on  their  contact  points,  and  the  question  arises  which 
reaction  will  occur  first.  The  law  of  the  gradual  reactions  states 
that  wherever  several  reactions  might  take  place,  the  first  reac- 
tion is  that  one  which  corresponds  to  the  least  stable  state,  then 
the  next  stable,  and  at  last  the  most  stable. 

In  our  case  we  have  but  two  possible  reactions :  The  formation 
of  C02  and  CO,  and  we  have  to  find  out  which  one  of  the  two  is 
more  stable.  We,  therefore,  have  to  consider  the  free  energies 
of  formation  of  the  two  compounds. 


PRODUCER  GAS  255 

Under  the  supposition  that  the  concentration  of  the  free  oxygen 
is  one  atmosphere,  we  find  that  the  curves  of  the  two  energies  of 
formation  go  through  the  same  point  at  a  little  below  1000°  abs. 
(about  700°  C.),  and  that  at  lower  temperatures  the  free  energy 
of  formation  of  the  C02  is  the  larger  one,  at  higher  temperatures, 
that  of  CO.  We  find  the  same  relation  in  the  stability  of  the  two 
compounds,  and,  therefore,  at  the  beginning  of  the  reaction  at 
low  temperatures  first  of  all  CO,  at  higher  temperatures  first  of 
all  C02,  will  be  formed.  In  rising  upwards  the  gases  will  further 
react  with  the  upper  layers  of  coal  and  with  the  air  contained  in 
the  interior  part  of  the  gas  current. 

The  reaction  of  the  outer  part  of  the  gas  current  with  coal  con- 
sists either  in  combustion  of  coal  by  means  of  C02  or  in  formation 
of  carbon  from  carbon  monoxide  (2  CO  =  CO2  +  C).  Since  at 
low  temperatures  first  of  all  CO,  is  formed,  the  most  plausible 
reaction  under  such  condition  is  the  decomposition  of  the  CO  and 
formation  of  C.  The  reaction,  however,  between  the  inner  and 
outer  parts  of  the  gas  current  counteracts  this  decomposition, 
since  the  0  of  the  inner  part  would  burn  any  C  which  was  depos- 
ited from  the  CO.  The  velocity  of  diffusion  and  mixture  between 
the  inner  and  outer  parts  of  the  gas  current  being  sufficiently 
large,  no  C  will  be  deposited ;  on  the  contrary,  the  CO  formed  will 
be  burned  to  C02,  and  the  oxygen  going  to  the  outer  part  will 
oxidize  some  more  carbon.  Therefore  the  average  composition 
of  the  gas  will  approach  more  and  more  the  equilibrium. 

At  higher  temperatures  at  first  C02  is  formed,  and  this  will,  by 
contact  with  the  higher  layers  of  coal,  oxidize  some  C  to  CO.  On 
the  other  hand,  the  oxygen  of  the  inner  part  will  tend  to  oxidize 
the  CO  present  to  C02. 

In  both  cases  we  have  two  effects  counteracting  each  other. 
At  low  temperatures  the  reaction  between  coal  and  the  outer  layer 
of  gas  tends  to  prevent  the  reaching  of  equilibrium,  while  the 
reaction  between  outer  and  inner  layers  favors  the  approach  to 
the  equilibrium.  At  high  temperatures,  however,  we  find  that 
the  reaction  between  gas  and  coal  favors  the  equilibrium,  and 
the  reaction  in  the  gas  current  works  against  it. 

The  conditions  become  still  more  complicated  if  we  consider 
that  the  actual  velocity  of  the  gas  current  at  different  points  of 
the  generator  varies  according  to  the  unequal  dimensions  of  the 
air  spaces,  and  that  also  the  temperature  throughout  the  genera- 


256 


HEAT  ENERGY  AND  FUELS 


tor  is  not  at  all  uniform.  If  the  generator  is  working  with  the 
fire  on  top  (maximum  temperature  in  the  upper  parts  of  the 
charge),  the  state  of  equilibrium  of  the  rising  gas  current  is  getting 
more  and  more  favorable  to  the  formation  of  CO. 

The  reverse  is  true  with  the  maximum  temperature  in  the 
lower  parts  of  the  producer.  The  location  of  the  maximum  tem- 
perature of  the  producer,  however,  changes  during  the  operation. 
In  starting  the  fire  the  upper  layers  of  the  generator  will  be  cold, 
and  will  allow  the  formation  of  C02.  They  are  gradually  heated 
up  by  radiation  of  heat  from  the  combustion  gases  to  the  coal, 
and  the  hot  zone  will  therefore  extend  from  the  bottom  further 
upwards.  After  continued  blowing  we  can  imagine  a  coke  col- 
umn which  has  the  combustion  temperature  of  the  hot  carbon  in 
cold  air. 

As  will  be  seen  from  the  above  considerations  the  research  of 
the  generator  process  is  extremely  difficult,  and  we  have  but  a  few 
scientific  investigations  on  this  subject.  One  of  the  best  is  by 
0.  Boudouard,  even  this  being  not  free  from  objectionable  points. 
He  passed  air  at  different  speeds  through  a  tube  filled  with  char- 
coal and  analyzed  the  gases  obtained.  He  found  at  800°  C.  the 
results  given  in  Table  CXIV : 


TABLE  CXIV. 
ANALYSIS  OF  PRODUCER  GAS.     (Per  Cent  by  Volume.) 


Gas. 

Flow  in  Liters  per  Minute. 

0.10 

0.27 

1.30 

1.4655 

3.20 

COo 

18.2 
5.2 

18.43 
3.8 
0.47 
77.30 

18.92 
1.88 
0.94 
78.26 

19.9 
1.83 

78~27 

19.4 
0.93 
0.93 

78.74 

CO"  

o 

N2  (difference)  

76.6 

The  analysis  corresponding  to  the  equilibrium  at  this  tempera- 
ture is 

C02  0 . 92  per  cent  by  volume, 
CO  34 . 32  per  cent  by  volume, 
N  74 . 76  per  cent  by  volume. 


PRODUCER  GAS 


257 


It  will  be  noticed  that  the  gases  from  Boudouard's  experiments 
are  very  high  in  C02  and  very  low  in  CO.  In  three  cases  they  also 
contain  free  oxygen.  This  is  in  accordance  with  the  fact  that  at 
800°  C.,  C02  is  less  stable  than  CO,  so  that,  therefore,  C02  must 
be  formed  first  and  the  gas  composition  is  approaching  the  equi- 
librium but  gradually. 

To  better  understand  these  conditions  we  are  going  to  decom- 
pose the  gases  into  the  elementary  components.  We  have  in 
22.42  liters  of  gas  the  amounts  given  in  Table  CXV. 

TABLE  CXV. 
ELEMENTARY  COMPONENTS  OF  PRODUCER  GAS. 


Flow  in 

Gram-atoms  C.  in 

Mol.  Oxygen 
in 

Prim- 

Liters per 

CO.. 

Total. 

ary 

Minute. 

C02. 

CO. 

Total. 

CO. 

Free. 

gen. 

Air. 

0. 

0.92 

34.32 

35.24 

0.92 

17.62 

18.54 

64.76 

83.30 

0.0 

18.2 

5.2 

23.4 

18.2 

2.6 

20.8 

76.6 

97.4 

0.27 

18.43 

3.8 

22.23 

18.43 

1.9 

0.47 

20.8 

77.30 

98.1 

1.30 

18.92 

1.88 

20.80 

18.92 

0.94 

0.94 

20.8 

78.26 

99.06 

1.465 

19.9 

1.83 

21.73 

18.9 

0.92 

20.18 

78.27 

98.45 

3.20 

19.4 

0.93 

20.33 

19.4 

0.47 

0.93 

21.20 

78.74 

99.94 

According  to  the  law  of  gradual  reaction  in  the  beginning,  a 
thin  layer  of  C02  is  formed,  which  then  oxidizes  the  coal  layer 
through  which  it  passes.  It  will,  therefore,  be  pretty  nearly 
correct  to  suppose  that  the  outer  layer  (surface)  of  the  gas  cur- 
rent will  have,  shortly  after  its  entrance  into  the  tube,  the  com- 
position which  corresponds  to  the  equilibrium.  In  this  case  the 
ratio  of  C02  to  C02  +  CO  must  be  equal  to  0.0261,  and  there  must 
have  been  formed  the  amounts  given  in  Table  CXVI : 

TABLE  CXVI. 


Flow  in 
Liters  per 
Minute. 

Vol.  CO2. 

Vol.  CO. 

Oxygen  in 
Same. 

Corresponding 
Amount 
of  Air. 

0.10 

0.61 

22.79 

12.01 

57.19 

0.27 

0.58 

21  65 

11.41 

54.33 

1.30 

0.54 

20.26 

10.67 

50.81 

1.465 

0.54 

20.19 

10.64 

50.67. 

3.20 

0.53      - 

19.80 

10.43 

49.67 

258 


HEAT  ENERGY  AND  FUELS 


If  we  deduct  the  air  volume  actually  used  for  the  original  com- 
bustion from  the  volume  of  primary  air,  we  get  the  surplus  quan- 
tity of  air  from  which  we  can  figure  by  a  simple  way  the  surplus 
air  given  in  Table  CXVII  and  Fig.  85. 


-5- 


012  8  Velocity 

FIG.  85.  —  Curve  of  Surplus  Air. 


TABLE  CXVII. 
SURPLUS  AIR  FOR  COMBUSTION. 


In  100  Volumes  Generator 

Of  100  Volumes 

Gas  Volumes  of 

Primary  Air. 

Flow  in  Liters 
per  Minute. 

N  Times 
Surplus 
Air. 

Primary 
Air. 

Air  for 
Original 
Combus- 

Surplus 
Quantity 

For 
Original 
Combus- 

Surplus 
Air. 

tion. 

tion. 

0.10 

97.40 

57.19 

40.21 

58.72 

41.28 

0.737 

0.27 

98.10 

54.33 

43.77 

55.38 

44.62 

0.805 

1.30 

99.06 

50.81 

48.25 

51.29 

48.71 

0.949 

1.465 

98.45 

50.67 

47.78 

51.46 

48.54 

0.943 

3.20 

99.94 

49.67 

50.27 

49.70 

50.30 

1.012 

The  following  consideration  will  be  still  more  useful  for  the 
practical  regulation  of  this  process: 


PRODUCER  GAS 


259 


We  suppose  again  that  in  the  first  moment  the  least  stable 
gas  is  formed,  but  that  in  a  short  time  on  the  surface  area  the 
equilibrium  corresponding  to  the  actual  gasifying  temperature 
will  be  reached.  In  the  further  course  of  the  process  this  equi- 
librium will,  however,  be  disturbed  by  the  gradual  mixture  of 
the  outer  gas  layer  with  the  inner  air  volume,  by  the  fall  in  tem- 
perature resulting  therefrom,  and  by  the  combustion  of  a  part  of 
the  original  CO  to  C02,  due  to  the  surplus  oxygen. 

Referring  again  to  Boudouard's  experiments  at  800°  C.,  we 
can  calculate  from  the  free  oxygen  content  of  the  gases  the 
corresponding  amount  of  air,  deduct  the  latter  from  the  com- 
position of  the  gas,  calculate  the  temperature  of  equilibrium 
corresponding  to  the  gas  mixture  obtained,  and  compare  the 
temperature  of  equilibrium  with  the  actual  gasifying  temper- 
ature (800°  C.  -  1073°  abs.).  We  obtain  thereby  the  results 
given  in  Table  CXVIII. 


TABLE  CXVIII. 

IDEAL  GASIFYING  TEMPERATURE,   ETC. 


• 

Flow  in  Liters  per  Minute. 

0 

0.10 

0.27 

1.30 

1.465 

3.9° 

Free  oxygen,  per  cent  by  vol.... 

0.47 

0.94 

0.93 

Corresponding  amount  of    air, 

per  cent  by  volume  

2.24 

4.48 

4.43 

Composition  of  the  gasfCO2  .... 

0^92 

18^2 

18.85 

19.81 

19.9 

20.20 

free  from  air,  per  cent-ICO  

34.32 

5.2 

3.89 

1.98 

1.83 

0.97 

by  volume                   |N2  

64.76 

76.6 

77.26 

78.21 

78.27 

78.74 

Gasifying  temperature  (absol.), 

corresponding    to    the    com- 

position   

1073° 

763° 

749° 

732° 

729° 

700° 

Difference  between   the   latter 

and  the  actual  gasifying  tem- 

perature, which  is  higher  by  .  . 

0° 

307° 

324° 

341° 

344° 

373° 

As  may  be  seen  from  Table  CXVIII  and  from  Fig.  86,  the 
" ideal"  (or  apparent)  gasifying  temperature  corresponding  to 
the  actual  composition  of  the  gas  is  clearly  below  the  actual,  and 
the  curve  of  this  difference  of  temperatures  consists  of  two  prac- 
tically straight  branches,  which  are  connected  with  each  other 


260 


HEAT  ENERGY  AND  FUELS 


by  a  short,  sharply  bent  curve.  In  the  one  branch,  which 
is  practically  vertical,  the  velocity  of  reaction  is  the  main  factor, 
while  in  the  inclined  branch  the  velocity  of  the  wind  is  of  main 
importance. 

Naturally,  the  position  and  shape  of  this  curve  depends,  not 
only  on  the  gasifying  temperature,  but  also  on  the  size  of  coal 
used,  and  on  the  height  of  the  fuel  layer.  Under  conditions, 
however,  which  can  be  compared  with  each  other,  these  additional 

factors  will  have  the  same 
character  and  the  position  of  the 
bending  point  of  the  curve  seems 
a  very  suitable  characteristic 
point  for  the  conditions. 

With  increasing  gasifying  tem- 
perature, the  velocity  of  reaction 
increases,  and  the  bending  point 
of  the  curve  will  move  to  the 
right.  Increase  of  the  fuel 
height  and  decrease  of  the  coal 
size  will  have  a  similar  effect. 
In  the  latter  cases,  however, 
some  other  influences  have  to 
be  considered,  such  as  friction 


FIG.  86.  —  Difference  of  Temperature 
between  Actual  and  Apparent  Gasi- 
fying Temperature. 


between  gas  current  and  coal 
pieces,  heating  of  the  upper  layers  by  the  rising  gas,  location 
of  the  maximum  temperature  in  the  generator,  etc. 

The  following  figures  are  given  as  practical  results  of  genera- 
tors that  were  charged  with  carbonized  fuel. 

Ebelman  gasified  at  Audincourt  small-sized  charcoal  in  a 
pressure  producer,  which  had  the  shape  of  a  small  blast  furnace, 
and  he  obtained  a  gas  of  the  following  composition  (per  cent  by 
weight) : 


CO  34.1  percent 

C02  0.8  per  cent 

N  64 . 9  per  cent 

H2 0.2  percent 

100.0  per  cent. 


PRODUCER  GAS  261 

In  a  gas  producer  at  Pous  1'Eveque,  which  was  charged  with 
coke,  he  obtained  a  gas  of  the  following  composition : 

CO     33. 8  per  cent 

C02   1.3  percent 

N 64 . 8  per  cent 

H2      0.1  per  cent 

100 . 0  per  cent. 

MIXED  DISTILLATION  AND  COMBUSTION  GASES. 

If  we  subject  natural  uncarbonized  fuel  in  proper  apparatus 
(gas  generators,  also  called  gas  producers)  to  incomplete  com- 
bustion, mixed  distillation  and  combustion  gases  are  formed. 
In  the  upper  layers  of  the  producer  the  hygroscopic  water  is 
removed.  In  further  going  downwards  the  fuel  (material  to  be 
gasified)  is  subjected  to  dry  distillation,  coke  being  the  result  of 
this  process.  The  coke  is  burned  incompletely  in  the  lowest 
part  of  the  producer,  whereby,  besides  the  heat  necessary  for 
evaporation  and  dry  distillation,  CO  is  also  generated.  The 
water  which  is  introduced  as  moisture  with  the  atmospheric  air 
is  also  decomposed.  A  clear  idea  of  these  processes  is  given  in 
the  table  below,  without,  however,  taking  into  account  the 
formation  of  tar,  which  is  inconsiderable. 

Composition  of  the  coal  used  (bituminous  coal  of  Ostrau, 
Moravia)  mixed  with  lignite  of  Leoben  (Styria). 

C  =  64.92 
H2=  2.50 
N  -  0.50 

Chemically  combined  water       14.22 

Hygroscopic  water       12.42 

Ash        5.44 


100.00 
Combustible  sulphur        0.52 

Calorific  value       6374  calories. 

(a)  Process  in  the  upper  part  of  the  generator  (drying  of  coal) : 
100  kg.  coal  yield  12.42  water  (steam),  and  87.58  kg.  dry  coal. 

(b)  Process  in  the  middle  part  of  the  generator  (dry  distilla- 
tion of  coal). 


262 


HEAT  ENERGY   AXD  FUELS 


TABLE  CXIX. 
ELEMENTARY    ANALYSIS    OF    COAL    AND    PRODUCTS    OF    DISTILLATION. 


87  .  58  Kg.  Dry  Coal 
Contain. 

Yield. 

Coke. 
Kg. 

Gases  of  Distillation  Kg. 

KO. 

CO. 

CH4. 

H,. 

NH3. 

H2S. 

Ash    . 

4.92 
64.92 
0.50 
0.52 
4.08 
12.64 

87.58 

4.92 
58.73 

0.12 

0.635 
5.08 

5^67 
7^56 

0^52 
0.17 

3.14 

0.50 

o.n 

0.40 
0.025 

C  
N  

S  
H, 

or::...:...:..:.: 

Sum  

63.77 

5.715 

13.23 

0.69 

3.14 

0.61 

0.425 

TABLE  CXX. 
ELEMENTARY  ANALYSIS  OF  COAL  AND  PRODUCTS  OF  COMBUSTION. 


Components  in 
Kg. 

Coke. 

Air. 

Sum. 

Yields. 

Losses 
thr'h 
Grate 
Open- 
ings. 

Gases. 

CO.. 

CO. 

H20. 

N. 

Ash.. 

4.92 
58.73 

211.63 

0.25 

64.49 

276.37 

4.92 
58.73 
211.63 
0.12 
0.25 
64.49 

4.92 
15.67 

6^57 

36*49 

0.25 

211^63 

c 

N. 

S  

H*°  lo*.:::::::: 

Sum 

0.12 

0.12 

0.25 

17.51 

48.65 

63.77 

340.14 

20.96 

24.08 

85.14 

0.25 

211.63 

We  suppose  that  the  coke  contains  nothing  but  carbon, 
besides  the  ash,  and  that  the  gases  of  dry  distillation  contain  no 
oxygen  except  as  CO  and  H20  (the  latter  supposition  is  not 
quite,  but  sufficiently  correct,  since  the  gases  contain  CC^  and 
other  oxygen  compounds).  The  formation  of  tar  is  not  taken 
into  consideration. 

Since  only  a  small  amount  of  N  is  present,  we  calculate  the 
entire  amount  as  NH3;  actually,  however,  but  one-fifth  of  the 
nitrogen  of  coal  is  transformed  into  NH3. 


PRODUCER  GAS 


263 


(c)  Process  on  and  just  above  the  grate  (incomplete  com- 
bustion of  the  coke  formed). 

The  coal  analysis  shows  5.44  per  cent  ash,  while  the  table  shows 
only  4.92  per  cent,  which  is  explained  by  oxidation,  mainly 
formation  of  sulphates  from  Fe2S.  The  composition  of  gas 
shown  in  the  last  table  results  from  the  average  composition  of 
generator  gas  and  the  composition  of  the  gases  of  distillation, 
which  is  given  in  Table  CXIX. 

The  distribution  of  heat  in  the  generator  is  shown  in  the  heat 
balance,  Table  CXXI. 


TABLE  CXXI. 

HEAT  DISTRIBUTION  IN  GENERATOR. 


Production  of  Heat  and  Non-Produced 
Heat. 

Single. 

Combined. 

Cal. 

Per 
Cent. 

Cal. 

Per  Cent. 

I.    Production  of  heat: 
1.    Heat  produced  in  generator  by 
chemical  processes  
2.    Heat  introduced  by  coal  and 
air  (by  their  temperature)  

II.    Non-produced  heat: 
1.    Unburned  coal  falling  through 
the  grate  .  . 

179666.4 
3337.9 

26.67 
0.49 

183004.3 
490641  .  6 

183004.3 
126613.6 

27.16 

72.84 

27.16 
18.79 

126613.6 
364028.0 

18.79 
54.05 

2.    Heat  capacity  of  generator  gases 

III.   Heat  losses: 
1.   By  fuel  and  ash  falling  through 
grate  
2.   By  heat  carried  away  by  the 
gas  produced  
3.    Loss  by  moisture  of  gas  
4.   By  decomposition  of  water.  .  .  . 
5.    (a)  Radiation  
(b)  Heat  necessary  for  gasify- 
ing coal  .  .  . 

2316.1 

28282.0 
12346.3 
8615.5 
94890.7 

36553.5 

0.34 

4.20 
1.83 
1.28 
14.09 

5.42 

IV.   Non-produced  heat: 
By     unburned       coal      falling 
through  grate  

Heat  gained  

309617.9 
364028.0 

45.95 
54.05 

673645.9 

100.00 

264 


HEAT  ENERGY  AND  FUELS 


It  is  understood  that  the  composition  of  generator  gas  depends, 
besides  the  quality  of  fuel,  on  the  size  of  same,  height  of  fuel 
layer,  construction  of  generator,  and  also  temperature  and  air 
pressure  during  the  operation.  Table  CXXI  was  prepared  by 
Richard  Akerman. 

TABLE  CXXII. 
GENERATOR  GAS   FROM  WOOD  OF  FIR  TREES. 


Trunks 

Kind  of  Fuel. 

and 
Roots. 

Brush- 
wood. 

Logwood. 

Sawmill 
Refuse. 

(  Thickness  m.m. 

20-35 

35-150 

20-200 

Size.  ] 

maximum 

maximum 

maximum 

(  Length  m.m. 

500-750 

200 

890 

340 

Contents: 

Hygroscopic  water,  per  cent  .  .  . 

12. 

16. 

27. 

60. 

Ash,  per  cent  

0.9 

Q.6 

0.5 

0.3 

Wood  substance,  per  cent  

87.1 

83.4 

72.5 

39.7 

Composition  of  wood  substance: 

C,  per  cent  

53.0 

? 

51.0 

? 

Hi  per  cent 

7.1 

*j> 

6  1 

9 

O,  per  cent  

39.8 

? 

\    294  \ 

? 

N,  per  cent  

0.1 

? 

\         4  i 

? 

Grate  area,  square  meter,  of  gen. 

0.0 

0.81 

1.72 

1.37 

Cubic  content,  cubic  meters,  of 

generator  

26.7 

1.9 

24.2 

7.4 

Consumption  of  fuel  per  dav  : 

Ccu  m 

8.  1 

23.8 

14.4 

Per  sq.  meter  grate  area  <    i  ' 

1654 

8891 

7909 

Per  generator  j  c£gm> 

65.2 
14866 

6.6 

1340 

41.0 
15293 

19.7 
10835 

Number  of  charges  per  24  hours.. 

2.8 

5.6 

4.1 

6.6 

Length  of  time  of  presence  of  fuel 

in  generator  (hours)  

8.6 

4.3 

5.9 

3.6 

Temperature  of  gas  leaving  gen- 
erator, degrees  C  

180° 

505° 

147° 

125° 

Kg.  tar  in  24  hours  

? 

? 

444 

? 

Composition  of  tar: 

C,  per  cent  

75.5 

H.2  per  cent  

7.4 

O.  per  cent  

16.6 

N.per  cent 

0.5 

Volume  composition  of  gases  free 

of  moisture  and  air: 

CO,. 

3.8 

6.2 

6.0 

11.3 

CO. 

29.8 

26.0 

29.8 

19.6 

CJL. 

0.6 

0.3 

0.9 

CH4  

4.2 

5.1 

6.9 

4.3 

H 

6.4 

4.3 

6.5 

7.4 

55.2 

58.4 

50.5 

56.5 

2 

PRODUCER  GAS 


265 


TABLE  CXXIII. 
GENERATOR  GAS   FROM   PEAT. 


Origin. 
Quantity  of  Peat. 

Munkfors 
Good  Fibrous 
Peat. 

Lotorp 
Good  Fibrous 
Peat. 

Hygroscopic  water,  per  cent  

25.0 

36.0 

^  -2  -|    Gases,  noncombustible  

8.3 

17.6 

^  ^  £?    Gases,  combustible. 

39.0 

16.9 

*  5  1    Fixed  carbon,  per  cent  

24.9 

24.0 

Ash,  per  cent  

2.8 

5.5 

,C,    per  cent  .  . 

57.8 

61.0 

Composition  of  peat  substance  JQ2'  P®J,  ^l^t  ' 

6.8 
34.0 

6.3 
30.6 

IN,    per  cent.. 

1.4 

2.1 

Grate  area,  square  meters  (    ,  ™pnprator 
Cubic  content,  cubic  meters.  .  .  \  ol  gen 

0.0 

22.8 

1.6 
21.9 

*  g  £  per  sq.  meter  grate  area  j  <*bio  meter  ; 

12.8 
5279 

&  iflPer  generator  j^^; 

20.6 
6262 

40.2 
8446 

Number  of  charges  per  24  hours  

1.3 

1.1 

Length  of  time  for  which  fuel  remains  in  gener- 

ator in  hours  

18.5 

21.8 

Temperature  of  gas  leaving  producer,  deg.  C  .  .  . 

86-100° 

75-105° 

Kg   tar  in  24  hours                   

152 

173 

rC 

79.6 

79.8 

f  H 

9.3 

I   "-1  { 

9.2 

9.6 
1.4 

Composition  of  tar  \  ^.2  " 

IN  

CO,,  vol.  per  cent  . 

6.6 

6.8  -  7.4 

co"  : 

29.6 

27.6  -26.2 

Composition  of  gas  free  of    C2H4 

0.7 
4.0 

0.4  -  0.4 
3.75-  3.70 

air  and  water  .  .        .....  1  CH4  

H2  

5.3 

12.3  -13.5 

N2  

53.8 

49.15-48.8 

TABLE  CXXIV. 

GENERATOR  GAS   FROM  BITUMINOUS  COAL. 


Intermediate  analysis. 


Hygroscopic  water,  per  cent 

Gases,  non-combustible,  per  cent 

Gases,  combustible,  per  cent 


Coked  coal,  per  cent 

Ash 

/C,    per  cent . . 

Composition  of  coal  substance  j^2'  ^  £|£*  ' 

\N,  per  cent . . 


7.6 

9.1 
13.6 
64.6 

5.1 
79.0 

5.9 
13.7 

1.4 


266 


HEAT  ENERGY  AND  FUELS 


TABLE  CXXIV.  —  Continued. 


Limestone  addition,  per  cent 


Residue  in  ash-pit 


eight  in  per  cent  of  coal 

C,  per  cent.  ...*... 
H9,  per  cent. .  . 


Composition 


O2  +  N2,  per  cent 

Ash 


. 

Grate  area,  square  meters,  of  generator  .................... 

Cubic  content,  cubic  meters,  of  generator  .................. 


Daily  consumption  of  coal  per 


Sq.  m.  grate  area  j  -^  m" 


Generator.  . 


(  Cu.  m.  ... 

I  Kg  ..... 

Number  of  charges  per  24  hours  ........................... 

Length  of  time  for  which  fuel  remains  in  generator  ......... 

Temperature  of  gas  leaving  generator,  deg.  C  .............. 

CO2,  vol.  per  cent 


Composition   of   gases   free   of   air    and 


water  .... 


CO 


2H4 

'H4 


3.4 

12.1 

40.2 

1.0 

1.2 

57.6 

2.0 

4.0 

1.7 

1251 

3.4 

2502 

1.2 

20 

500° 

1.8 

27.3 

0.4 

4.2 

6.2 

60.1 


TABLE  CXXV. 

GENERATOR  GAS   FROM  LIGNITE. 

Below  are  given  results  with  a  lignite  generator: 

Number  of  generators 3 

Grate  area  per  generator. 2.5  square  meters 

Duration  of  test 12      hours  45  minutes 

Coal  charged 3600      kg.  Leoben  (Styria)  coal 


Composition  of  coal 


Calorific  value 


C.. 

Volatile  H2, 

N 

H2O  chemically  combined . 


H2O  hygroscopic 9 . 34 


61.72  per  cent 
1.85  per  cent 
0.22  per  cent 

20.09 


Ash 
Combustible  S , 


6.78 
0.37 
5446  kg.  cal. 


Losses  through  grate  .  .  .  

936.7    kg. 

Composition  of  losses  <  A  '  i  '   ' 
(  Asn  

73.94  per  cent. 
26.  06  per   cent. 

Aver- 

1 

2 

3 

4 

age. 

CO2,  vol.  per  cent 

5.3 

5.4 

4.2 

4.4 

4.64 

02, 

0.3 

0.8 

0.6 

0.8 

0.65 

Composition  of  dry 
generator  gas  .  .  . 

CO, 
CH4, 

25.19 
0.29 

25.05 
0.15 

25.39 
0.51 

26.50 
0.40 

25.59 
0.38 

^2> 

10.29 

10.65 

11.29 

11.60 

11.11 

N9 

58.63 

57.95 

58.01 

56.30 

57.63 

PRODUCER  GAS  267 

TABLE  CXXVI. 

QUANTITY  GASIFIED  PER  HOUR  AND   SQUARE  METER  GRATE 

AREA. 

Logwood  and  sawdust  mixed 45-  50   kg. 

Sawmill  waste 200-330 

Logwood 370 

Loose  peat  (bad  quality) 75-120 

Good  fibrous  peat 200-250 

Lignite 40-50 

Bituminous  coal 60-250 

SUGGESTIONS  FOR  LESSONS. 

Air  (generator)  gas  has  to  be  made  in  a  small  experimental 
producer  using  different  grades  of  fuel,  varying  height  of  fuel 
layer  and  air  of  different  pressures.  Gas  and  fuel  is  to  be 
analyzed,  the  quantity  of  the  fuel  consumed  and  of  the  gas 
generated  to  be  found  and  the  balance  of  the  process  to  be  put 
up.  The  results  are  to  be  compared  with  the  ideal  process. 

On  a  small  scale  (in  glass  and  porcelain  tubes)  experiments 
can  be  made  for  demonstrating  the  influence  of  the  length  of 
the  tube  (fuel  height)  and  velocity  of  the  wind. 


CHAPTER  XXI. 


WATER  GAS. 

INSTEAD  of  producing  fuel  gases  by  the  action  of  the  oxygen 
in  the  air  on  glowing  coal,  we  can  use  for  this  purpose  the  oxygen 
of  water  in  place  of  the  oxygen  in  the  air. 

If  steam  is  led  over  glowing  coal,  two  different  reactions  will 
take  place  depending  on  the  temperature.    At  very  high  tem- 
peratures the  reaction  takes  place  according  to  the  equation 
C  +  H20  =  CO  +  H2, 

while  with  decreasing  temperature  a  second  reaction  becomes 
more  and  more  prevalent  according  to  equation 
C  +  2  H20  =  C02  +  2  H2. 

The  first  equation  is  furnishing  a  mixture  of  equal  volumes 
of  CO  and  H2,  CO  50  per  cent  by  volume  and  H2  50  per  cent  by 
volume,  while  the  second  reaction,  if  taking  place  exclusively, 
furnishes  a  gas  containing  two  volumes  H2  for  every  one  volume 
of  C02,  hence  C02  33.33  per  cent  by  volume  and  H2  66.67  per 
cent  by  volume.  The  thermal  value  of  the  first  gas  per  22.42 
liters  is  68  cal.,  of  the  second  gas,  45.4  cal. 

A  comparison  of  the  generator  (air)  gas  process  with  the  two 
-water  gas  processes  shows : 

TABLE  CXXVII. 

PRODUCER  AND  WATER  GAS  PROCESSES. 


Volume  Per  Cent. 

H2. 

CO. 

C02. 

N2. 

Thermal 
Value  of 
1  Volume. 
Cal. 

Of  Mix- 
ture at 
Constant 
Pressure. 
Cal. 

lC+i(O2)-2N2=CO-f2N 

33£ 

66$ 

22.6 

22.9 

2C+2H2O=CO2X2H2 

66§ 

33£ 

45.4 

46.5 

3  C+H2O=CO+H2 

50 

50 

68.0 

68.5 

268 


WATER  GAS 


269 


The  figures  of  thermal  value  refer  to  the  same  gas  volume  in 
each  case,  and  are  well  adapted  for  comparing  the  qualities  of 
the  gases.  In  case,  however,  we  want  to  consider  the  utilization 
of  fuel,  we  have  to  refer  the  thermal  values  to  equal  quantities 
of  carbon  (equal  volumes  of  CO  and  C02) ,  and  we  obtain : 


12  Grams  C. 
Yield  Liters 
of  Gas. 

Value  of  the  Gas  at 
Constant 

Volume. 

Pressure. 

2 
3 

67.26 
67.26 
44.84 

67.  Seal. 
113.3cal. 
125.8  cal. 

68.  7  cal. 
116.1  cal. 
126.8  cal. 

We  see  that  water  gas  even  under  the  most  unfavorable  cir- 
cumstances yields  more  heat  (thermal  value)  than  the  ideal  air 
(generator)  gas,  besides  the  fact  that  it  contains  less  non-com- 
bustible gases. 

For  making  a  perfect  comparison  we  have  to  calculate  at  least 
—  if  not  the  pyrometric  heating  effect  —  the  quantity  of  air 
theoretically  required  for  combustion.  We  have  for  each  22.42 

liters  of  gas : 

TABLE  CXXVIII. 
COMPOSITION  OF  PRODUCER  AND  WATER  GASES. 


Composition  of  Gas 
in  Per  Cent  by  Volume. 

Theoretical 
Amount 
of  Air 

Combus- 
tible In- 

Products of 
Combustion. 

different 

H2. 

CO. 

C02. 

N2. 

02. 

N2. 

Gases. 

H2O. 

C02. 

N2. 

1 

33$ 

66* 

16* 

64^ 

33$  131$ 

33$ 

66§ 

2 

66§ 

33$ 

33$ 

133$ 

66§  166§ 

66§ 

33$ 

133$ 

3 

50 

50 

50 

200 

100     200 

50 

50 

200 

As  the  decomposition  of  water  requires  more  heat  than  is 
furnished  by  the  formation  of  CO,  and  even  CO2,  both  water  gas 
processes  are  taking  place  only  with  the  assistance  of  external 
heat.     We  have 
C  +  i  (02)  =  CO  +  28,900  cal. 
C  +  2  H20  =  C02  +  2  H2  +  97,600  -  116,120  =  CO2  +  2  H2 

-  18.5  cal. 

C  +  H20     =  CO  4-  H2  +  28,900  -  58,060  =  CO  +  H2  -  29.2 
cal. 


270 


HEAT  ENERGY  AND  FUELS 


Considering  the  external  heat  we  have: 


Thermal 

Value  of 
Gas  per  12 
Grams  C. 

External 
Heat  to  be 
Supplied. 

Gain  in 

Heat. 

C+*(02)  +  2N2=CO+N., 

68.  7  cal. 

-28.  9  cal. 

97.6 

C  +  2H2O=CO,+  2H2  
C+H2O=CO+H2  

116.1  cal. 
126.8  cal. 

+  18.5  cal. 
+  29.  2  cal. 

97.6 
97.6 

The  advantage  of  water  gas,  therefore,  does  not  consist  in  a 
gain  in  heat,  but  exclusively  in  the  higher  thermal  value  of  this 
gas,  which  allows  a  better  utilization  in  the  combustion. 

As  can  be  seen  from  the  above  statements,  the  reaction, 
C  -h  H20  =  CO  +  H2,  will  take  place  if  steam  is  led  through  a 
layer  of  sufficiently  hot  coal..  As  heat  is  absorbed  by  this  reac- 
tion, the  coal  will  cool  off,  and  besides  the  above  reaction,  the 
process  C  +  2  H20  =  C02  +  2  H2  will  take  place.  As  the  cool- 
ing continues  the  second  process  will  begin  to  outweigh  the  first, 
and  finally,  since  the  second  reaction  also  absorbs  heat,  the  coal 
will  be  so  cold  that  the  reaction  will  stop,  and  thus  the  steam  will 
go  through  the  fuel  undecomposed. 

This  necessitates  reheating  the  coal  in  the  generator.  This  is 
done  by  shutting  off  the  steam  and  blowing  air  through  the 
generator  until  the  coal  is  sufficiently  hot.  During  this  period 
air  (generator)  gas  is  produced  which  can  be  utilized  independent 
of  the  water  gas.  This  period  is  called  "hot-blowing."  As  soon 
as  the  coal  is  hot  again,  the  air  blast  is  stopped  and  the  steam 
valve  opened,  and  water  gas  is  made  until  the  cooling  off  of  the 
fire  again  prevents  the  rational  production  of  water  gas. 

We  have  here,  therefore,  an  intermittent  process,  which  not 
only  requires  careful  supervision  but  also  the  erection  of  double 
the  number  of  generators  in  places  where  a  continuous  stream 
of  water  gas  is  required,  and  where  a  large  gas  holder  is  objec- 
tionable. 

As  we  have  seen,  the  two  water  gas  reactions  are  taking  place 
in  parallel.  Since,  however,  the  one  furnishes  a  superior  gas  with 
better  utilization  of  coal  than  the  other,  it  is  of  importance  to 
know  the  conditions  which  determine  to  which  extent  each  of  the 
two  reactions  will  take  place.  For  this  purpose  we  have  to  study 
the  state  of  equilibrium  between  the  two  reactions. 


WATER  GAS  271 

To  find  the  equilibrium  of  the  gas  phase,  we  have  to  consider 
the  reactions  that  are  taking  place.     If  we  deduct 

C  +  H20  =  CO  +  H2 

from 

C  +  2  H20  =  C02  +  2  H2, 

we  get 

C02  +  H2  <=»  CO  +  H20. 

This  is  a  reversible  reaction  in  which  two  volumes  (CO  +  H20) 
are  formed  from  two  volumes  (C02  +  H2).  It  is,  therefore, 
independent  of  pressure  at  all  temperatures  above  the  boiling 
point  of  water.  One  might  now  conclude  that  the  composition 
of  water  gas  at  a  given  temperature  is  independent  of  the  pressure  ; 
this,  however,  is  not  correct.  From  the  last  equation  we  get  for 
the  isothermic  equilibrium 

Ceo,  .  CH,O          Ceo  Cn2 

or 


x  4 

Cco2  .  Cn2  Cco2         1  Cn2o 

We  therefore  see  that  at  a  given  temperature  there  is  corre- 

PO  TT 

spending   to   every  -   -  a   different  r—  -pr  .     To   reach   definite 

CO2  H2O 

results  we  have  to  look  for  a  reaction  which  determines  the  equi- 
librium between  the  gas  phase  (in  our  case  consisting  of  C02,  CO, 
H2  and  H20)  and  the  solid  phase  (C),  and  as  such  we  are  going  to 
use  the  equation  mentioned  already  in  the  generator  gas  process  : 

C02  4-  C^±2CO; 
from  this  equation  we  have 


Ceo 


And  now  the  conditions  are  given  for  calculating  the  isothermic 
equilibrium.  As  the  last-mentioned  reaction  depends  on  the 
pressure,  we  must  necessarily  conclude  that  the  composition  of 
water  gas  also  depends  on  the  pressure. 

We  are  going  to  discuss  now  the  theory  of  the  water  gas  process 
in  a  few  words.  If  we  express  the  steam  pressure  by  P  and  the 
gasifying  temperature  (in  degrees  C.),  by  t,  the  ideal  composi- 
tion of  the  water  gas  (i.e.,  the  composition  corresponding  to  the 
equilibrium  reached)  is  as  follows: 


272 


HEAT  ENERGY  AND  FUELS 


TABLE  CXXIX. 
EFFECT  OF  STEAM  PRESSURE  AND  TEMPERATURE  ON  COMPOSITION  OF  GAS. 


Vol.  Per 
Cent.        0.1 


0.25      0.5 


Steam  Pressure,  P,  in  Atmospheres. 
0.75       1.0         1.5        2.0        2.5        3^0 


4.0        5.0       10.0 


CO.. 

0.24 

0.12 

0.06 

0.04 

t  =  400°C. 
0.03      0.02 

0.02 

0.01 

0.01 

0.01 

0.01 

0.00 

CO2 

10.88 

7.86 

5.97 

5.04 

4.46      3.73 

3.27 

2.97 

2.73 

2.40 

2.15 

1  55 

H2?.... 
H2O 

....  21.99 
66  88 

15.84 
76.18 

11  99 
81.98 

10.12 
84.80 

8.94      7.48 
•86.57     88.77 

6.56 
90.15 

5.94 
91.08 

5.47 
91  .79 

4.82 
92.77 

4.31 
93.53 

3.11 

95.34 

t  =  600°C. 

CO... 

CO2 

....  26.66 

12  84 

18.87 
16  06 

14  65 
17  15 

11.56 
17  79 

10.03      8.14 
17  86     17  67 

6.99 
17  41 

6.20 

17  12 

5.61 
16  84 

4.78 
16  32 

4.22 
15  88 

2.87 
14  32 

H2  
H20.... 

..  52.34 
....     8.16 

50.89 
14.18 

48.95 
19.25 

47.14 
23.51 

45.75     43.48 
26.36    30.71 

41.81 
33.79 

40  44 
36.24 

39.29 
38.26 

37.42 
41.48 

35:  99 
43.91 

3K5I 
51.30 

t  =  800°C. 

CO  
C02.... 
H2  
H20.... 

..  49.04 
....     0.50 
....  50.03 
....     0.43 

47.81 
1.13 
50.07 
0.99 

46.04 
2.02 
50.03 
1.86 

44.46 
2.80 
50.06 
2.68 

43.05    40.56 
3.48      4.66 
50.02    49.88 
3.44      4.90 

38.53 
5.59 
49.71 
6.17 

36.83 
6.34 
49.51 
7.32 

35.41 
6.95 
49.21 
8.43 

32.81 
8.02 
48.85 
10.32 

30.69 
8.88 
48.45 
11.08 

24.38 
11.05 
46.48 
18.09 

t~iooo°c. 

CO  
C02.... 
H2  
H2O 

....  50.00 

::::  56:60' 

50.00 
56:66 

50.00 
56:66 

50.00 
50.66 

50.00    49.42 
0.25 
50.00    49.92 
...       0.41 

49.42 
0.25 
49.92 
0.41 

49.00 
0.45 
49.90 
0.65 

48.57 
0.61 
49.79 
1.03 

48.35 
0.71 
49.77 
1.17 

47.98 
0.87 
49.72 
1.43 

46.24 
1.59 
49.42 
2.75 

CO 

50  00 

50.00 

50.00 

50.00 

t=1200°C. 
50.00     50.00 

50.00 

50.00 

50.00 

49  32 

49  31 

49  31 

C02.... 

H2  
H2O 

::::  56:06 

56:66 

50:06 

50:66 

56:66    56:66 

50:66 

56:66 

56:66 

0^5 
49.82 
0.61 

0^5 
49.80 
0.64 

0^5 
49.80 
0.64 

t=!400°C. 

CO  
CO2.... 
H2  
H20.. 

....  50.00 

50.00 

50:06 

50.00 
56:06 

50.00 
56:06 

50.00     50.00 
56:66    56:66 

50.00 
56:66 

50.00 

50:66 

50.00 
56:06 

50.00 

50:06 

50.00 

50:66 

50.00 

50:00 

Figs.  87  and  88  show  the  ideal  composition  of  water  gas  at  a 
steam  pressure  of  one  and  four  atmospheres.  We  see  from  the 
diagrams  that  with  increasing  pressure  the  curves  are  moving 
towards  higher  temperatures.  We  also  see  that  the  quantity  of 
undecomposed  steam  present  is  rapidly  decreasing  from  a  certain 
temperature  on,  while  the  quantity  of  CO  and  H2  is  rapidly 
increasing  in  the  same  manner.  The  curves  of  CO  and  H2  are 
in  their  middle  part  practically  parallel,  but  the  upward  move- 
ment of  the  H-curve  is  beginning  200°  C.  below  the  bend  of  the 
CO  curve. 

The  C02  curve  starts  to  rise  together  with  the  H-curve  (but 
more  slowly),  until  it  crosses  the  steam  curve  and  falls  with  the 
latter.  The  result  of  this  discussion  for  practice  is  that  the 
most  favorable  gasifying  temperature  is  between  temperature 
limits  of  about  200°,  and  increases  with  the  steam  pressure. 


WATER  GAS 


273 


£§       8 


&Pot 


e        §        s         9 


s 


11 


.3 


I  L 


S3  o    o 


274 


HEAT  ENERGY  AXD  FUELS 


Vol.% 


°200        300         400         500         600         700         800         900        1000         1100      1200 

Temperature  in  cleg.  cent. 
FIG.  89.  —  Combustible  Gases  Present  in  Water  Gas. 


WATER  GAS 


275 


This  becomes  clearer  when  we  calculate  the  quantity  of  com- 
bustible gases  (CO  and  H2)  present  in  water  gas  (Fig.  89). 

TABLE  CXXX. 
QUANTITY   OF  COMBUSTIBLE   GASES   PRESENT  IN   IDEAL  WATER  GAS. 


Steam  Pressure 
in  Atm. 

Gasifying  Temperature  in  Degrees  Cent. 

400 

600 

800 

1000 

1200 

1400 

0.1  
0.25  
0.5  
0.75  
1.0  
1.5  
2.0  
2.5  
3  0 

22.23 
15.96 
12.05 
10.16 
8.97 
7.50 
6.58 
5.95 
5.48 
4.83 
4.32 
3.11 

79.00 
69.76 
63.60 
58.70 
55.78 
51.62 
48.80 
46.64 
44.90 
42.20 
40.21 
34.38 

99.07 
97.88 
96.12 
94.52 
93.08 
90.44 
88.24 
86.34 
84.62 
81.66 
79.14 
70.86 

100.00 
100.00 
100.00 
100.00 
100.00 
99.34 
99.34 
98.90 
98.36 
98.12 
97.70 
95.66 

100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
99.14 
99.11 
99.11 

100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 
100.00 

4.0  
5.0  
10.0  

As  the  combustion  of  one  mol  CO  yields  68,600  cal.,  the  com- 
bustion of  one  mol  H2  to  liquid  water  68,400  cal.,  which  is  prac- 
tically the  same  amount  of  heat,  we  can  use  the  above  table  for 
comparing  the  thermal  value  of  the  different  gases.  As  one  mol 
of  every  gas  at  0°  and  760  min.  pressure  occupies  a  space  of  22.42 
liters,  we  can  calculate  the  thermal  value  of  1  cubic  meter  of  the 
above  gases  in  large  calories  by  multiplying  their  content  of  com- 
bustible gases  with 

1000  X  68.5    _ 

100  X  22.42 


THERMAL  VALUE  OF 


TABLE  CXXXI. 

CUBIC  METER  OF  IDEAL  WATER  GAS  IN  KG.  CAL. 


Gasifying  Temperature  in  Degrees  Cent. 

Steam  Pressure 

in  Atm. 

400 

600 

800 

1000 

1200 

1400 

0.1  

680 

2417 

3032 

3060 

3060 

3060 

0.25  

590 

2135 

2995 

3060 

3060 

3060 

0.5  

369 

1946 

2941 

3060 

3060 

3060 

0.75  

311 

1715 

2892 

3060 

3060 

3060 

1.0  

274 

1707 

2848 

3060 

3060 

3060 

1.5  

230 

1580 

2767 

3040 

3060 

3060 

2.0  

201 

1493 

2700 

3040 

3060 

3060 

2.5  

182 

1427 

2642 

3026 

3060 

3060 

3.0  

168 

1374 

2589 

3010 

3060 

3060 

4.0  

148 

1353 

2499 

2002 

3034 

3060 

5.0  

132 

1230 

2422 

2990 

3033 

3060 

10.0  

95 

1052 

2168 

2927 

3030 

3060 

276 


HEAT  ENERGY  AXD  FUELS 


This  table  shows  more  clearly  that  the  thermal  value  of  the 
ideal  water  gas  increases  with  increasing  temperature  and 
decreases  with  increasing  pressure. 


Vol-% 
100 


90 


40 


30 


•20 


"200        300        400          500         600          700         800         90  000       1100       1200 

Temperature  in  deg.  cent. 
FIG.  90.  —  Undecomposed  Steam  in  Water  Gas. 

At  a  steam  pressure  of  1  to  2  atmospheres  the  most  favorable 
gasifying  temperature  is  between  800°  and  1000°  C.,  and  at  10 
atmospheres  pressure  between  1000°  and  1300°  C.  It  is,  there- 
fore, not  advisable  to  use  steam  of  too  high  pressure. 


WATER  GAS 


277 


The  quality  of  the  water  gas  is  deteriorated  by  its  content  of 
undecomposed  steam  and  of  C02.  We,  therefore,  will  consider 
the  influence  of  pressure  and  temperature  on  the  quantity  of  H20 
and  C02  present  in  the  gas. 

The  quantity  of  undecomposed  steam  in  the  ideal  water  gas 
decreases  rapidly  (Fig.  90)  with  increasing  gasifying  tempera- 
ture and  slowly  increases  with  the  pressure.  As  thereby  the 


600  700  800          900 

Temperature  in  deg.  cent, 
FIG.  91.  —  CO,   in  Water  Gas. 


looo       uoo      1200 


inflammability  of  the  gas  is  decreased,  the  gasifying  temperature 
should  not  be  below  700°  to  800°  C.,  with  a  steam  pressure  of  1  to 
10  atmospheres,  since  otherwise  the  quantity  of  undecomposed 
steam  will  be  considerably  above  10  per  cent  by  volume. 

The  content  of  C02  (Fig.  91)  is  injurious,  as  it  causes  an  unfa- 
vorable utilization  of  the  carbon.  Moreover,  it  deteriorates  the 
gas,  increasing  the  quantity  of  non-combustibles  and  lowering 
the  temperature  of  combustion.  As  the  C02  amounts  only  to  a 
few  per  cent  at  600°  to  700°  C.,  it  does  not  have  to  be  considered 
in  the  production  of  generator  gas. 


278 


HEAT  ENERGY  AXD  FUELS 


In  practice,  however,  it  is  of  importance  to  know  the  quantities 
of  carbon  and  steam  which  are  required  for  the  formation  of 
1  cubic  meter  of  water  gas.  This  information  is  given  in  the 
following  tables: 


TABLE  CXXXII. 

QUANTITY   OF   STEAM  IN  CU.   M.  REQUIRED   FOR  THE   FORMATION   OF 
1    CU.  M.  OF  IDEAL  WATER  GAS. 


Steam  Pressure 
in  Atm. 

Gasifying  Temperature  in  Degrees  Ce.it. 

400 

600 

800 

1000 

1200 

1400 

0.1  
0.25  
0.5  

0.8887 
0.9202 
0.9397 
0.9492 
0.9551 
0.9625 
0.9671 
0.9702 
0.9726 
0.9759 
0.9784 
0.9845 

0.6050 
0.6057 
0.6820 
0.7065 
0.7211 
0.7419 
0.7560 
0.7668 
0.7755 
0.7890 
0.7990 
0.8280 

0.5046 
0.5106 
0.5194 
0.5274 
0.5346 
0.5478 
0.5588 
0.5683 
0.5764 
0.5917 
0.6043 
0.6457 

0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5033 
0.5033 
0.5505 
0.5092 
0.5094 
0.5115 
0.5217 

0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5043 
0.5044 
0.5044 

0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 
0.5000 

0.75  
1.0  
1.5  
2.0  
2.5  
3.0  

4  0  

5  0 

10.0  

TABLE  CXXXIII. 

THEREFORE  ONE  CUBIC  METER  OF  STEAM  FURNISHES   THE  FOLLOWING 
NUMBERS  OF  CUBIC  METERS  OF  IDEAL  GAS. 


Steam  Pressure 
in  Atm. 

Gasifying  Temperature  in  Degrees  Cent. 

400 

600 

800 

1000 

1200 

1400 

0.1  
0.25  
0.5  

1.125 
1.087 
1.068 
1.053 
1.047 
1.039 
1.034 
1.031 
1.028 
1.024 
1.022 
1.015 

1.653 
1.537 
1.466 
1.415 
1.386 
1.348 
1.323 
1.304 
1.289 
1.269 
1.251 
1.208 

.981 
.958 
.925 
.896 
.871 
.825 
1.789 
1.759 
1.735 
1.690 
1.655 
1.548 

2.000 
2.000 
2.000 
2.000 
2.000 
1.986 
1.986 
1.978 
1.963 
1.963 
1.955 
1.916 

2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
1.983 
1.982 
1.982 

2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 

0.75  
1.0  
1.5  
2.0  
2  5 

3  0 

4.0  . 
5.0  
10.0  

WATER  GAS 


279 


The  last  table  is  specially  valuable  for  this  practice,  since  it 
permits  an  easy  control  of  the  operation  of  the  generator  and 
allows  the  determination  of  the  ideal  gasifying  temperature, 
which  corresponds  to  the  process.  The  content  of  one  component 
of  the  gas,  for  instance  C02  (which  can  be  easily  determined  with 
an  Ados  or  Strache  apparatus)  being  known,  the  complete  analy- 
sis of  the  gas  can  be  found. 

TABLE  CXXXIV. 

ONE  CUBIC  METER  OF  WATER  GAS  CONTAINS  GRAMS  OF  C. 


Steam  Pressure 
in  Atm. 

Gasifying  Temperature  in  Degrees  Cent. 

400 

600 

800 

1000 

1200 

1400 

0.1  
0.25  
0.5  
0.75  
1.0  
1.5  
2.0  

59.51 
42.71 
32.27 
27.19 
24.03 
20.07 
17.61 
17.05 
14.66 
12.90 
11.56 
8.30 

211.40 
186.95 
170.19 
157.08 
149.27 
138.14 
130.59 
124.81 
120.15 
112.93 
107.58 
91.96 

265.14 
261.23 
257.22 
252.94 
249.08 
242.07 
236.13 
231.05 
226.71 
218.52 
211.78 
189.62 

267.60 
267.60 
267.60 
267.60 
267.60 
265.83 
268.83 
264.66 
263.21 
262.57 
261.45 
255.99 

267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
265.30 
265.25 
265.25 

267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 
267.60 

2.5  

3.0  
4.0  
5.0  
10.0  

TABLE  CXXXV. 

ONE  CUBIC  METER  OF  STEAM  GASIFIES  GRAMS  OF  C.      (Fig.   92). 


Steam  Pressure 
in  Atm. 

Gasifying  Temperature  in  Degrees  Cent. 

400 

600 

800 

1000 

1200 

1400 

0.1.  . 
0.25  
0.5  
0.75  
1.0  
1.5  
2.0  
2.5  
3.0  

66.96 
46.41 
34.81 
28.64 
25.16 
20.85 
18.21 
17.57 
15.07 
13.22 
11.81 
8.43 

349.44 
287.30 
249.54 
222.34 
207.00 
186.19 
172.74 
162.77 
154.93 
143.13 
134.64 
115.06 

525.44 
511.61 
495.23 
479.59 
465.92 
441.89 
420.77 
406.54 
393.32 
369.31 
350.45 
293.67 

535.20 
535.20 
535.20 
535.20 
535.20 
528.17 
528.17 
523.56 
516.91 
511.52 
511.14 
490.68 

535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
526.17 
525.87 
525.87 

535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 
535.20 

4.0  
5.0.  
10.0  

280 


HE  AT  ENERGY  AND  FUELS 


If  the  steam  of  the  gas  condenses  —  which  frequently  happens 
in  practice  —  the  composition  and  thermal  value  of  the  gas 
changes  accordingly.  The  calculation  of  the  gas  composition 
from  the  C02  content  is  very  simple.  The  C02  of  the  dry  gas 
being  c  per  cent  by  volume,  the  content  of 

Q 

CO  =  50  -  -  c  per  cent  by  volume, 


H2  =  50  +  -  c  per  cent  by  volume. 


,200         300        400       500        600        700        800       900       1000      1100     .1200    1300 
Temperature  of  gas_in_deg.  cent 

FIG.  92.  —  Gasification  of  Carbon  by  Steam. 

For  example,  we  take  a  gas  made  at  800°  C.  and  2.5  atmospheres 
steam  pressure.  The  C02  content  having  been  found  as  6.84 
per  cent  by  volume,  the  content  of 

CO  =  50  -  1.5  X  6.84  =  39.74  per  cent  by  volume, 
H2    =  50  +  0.5  X  6.84  =  53.42  per  cent  by  volume. 

The  following  two  tables  contain  the  most  important  data  on 
dry  water  gas.  Compared  with  the  wet  gases,  in  which  at  con- 
stant pressure  the  C02  content  at  first  increases  with  the  tem- 
perature up  to  a  maximum  and  then  decreases,  the  dry  gases 
have  far  more  regular  properties.  The  C02  content  at  constant 
pressure  decreases  with  increasing  temperature,  while  CO  and  H2 
increase  simultaneously.  On  the  other  hand  C02  increases  at 


constant   temperature   with 
decrease  simultaneously. 


the   pressure,   while   H2   and   CO 


WATER  GAS 


281 


TABLE  CXXXVI. 
QUANTITY  OF  DRY  GAS  PRODUCED  FROM  ONE  CUBIC  METER  OF  STEAM. 


Steam  Pressure 
in  Atm. 

One  Cubic  Meter  of  Steam  is  Yielding,  at  the  Temperatures 
Stated  Below,  Cubic  Meters  Dry  Water  Gas. 

400°  C. 

600°  C. 

800°  C. 

1000°  C. 

1200°  C. 

1400°C. 

0.1  
0.25  
0.5  

0.373 
0.259 
0.192 
0.160 
0.141 
0.117 
0.102 
0.092 
0.084 
0.074 
0.066 
0.047 

1.518 
1.304 
1.184 
1.082 
1.021 
0.934 
0.876 
0.831 
0.796 
0.743 
0.702 
0.588 

1.972 
.939 
.889 
.845 
.807 
.736 
.679 
.630 
1.589 
1.516 
1.457 
1.268 

2.000 
2.000 
2.000 
2.000 
2.000 
.978 
.978 
.965 
.943 
.940 
.927 
.863 

2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
1.971 
1.969 
1.969 

2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 
2.000 

0.75  
1.0  

1.5  
2.0  
2.5  
3.0  
4.0  
5.0  

10.0  

The  most  favorable  conditions  for  producing  the  dry  water 
gas  are  therefore  the  same  as  for  the  wet  gas.  We  have  so  far 
discussed  the  case  in  which  the  state  of  equilibrium  is  actually 
reached  in  the  producer.  We  are  now  going  to  consider  the  case 
which  is  very  common  in  practice,  that  the  equilibrium  is  not 
reached. 

If  steam  is  blown  through  a  layer  of  glowing  coal  the  reaction 
will  undoubtedly  take  place  completely  on  the  contact  points  of 
steam  and  coal,  i.e.,  the  state  of  equilibrium  will  soon  be  reached 
here.  On  its  further  way  the  gas  current  will  undergo  a  change 
in  two  respects.  Partly  by  diffusion,  partly  by  mechanical 
mixture,  a  reaction  will  take  place  between  the  outer  part  of  the 
current  and  the  inner  part,  which  is  richer  in  steam ;  on  the  other 
hand,  the  equilibrium  of  the  outer  layer  will  be  disturbed  by  the 
contact  of  same  with  other  parts  of  the  coal. 

If  the  gas  passes  from  the  cold  to  the  hot  coal  layers  ("Ge- 
genstrom"),  a  gas  rich  in  C02  will  be  formed  at  first  in  the  outer 
layer;  then,  by  coming  in  contact  with  hot  coal,  it  is  enabled  to 
oxidize  new  quantities  of  coal,  getting  thereby  richer  in  CO.  If, 
however,  the  steam  passes  from  the  hot  to  the  cold  coal  layers 
("Parallelstrom"),  a  gas  rich  in  CO  will  be  formed  at  first  in  the 
outer  layer,  and  by  passing  further  it  will  get  richer  in  C02  and 
poorer  in  CO. 


282 


HEAT  ENERGY  AXD  FUELS 


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WATER  GAS  283 

We  will  now  consider  again  the  reaction  between  the  outer 
gas  layer  and  the  inner  steam  current.  In  working  according 
to  the  "Gegenstrom  principle,"  the  steam  of  the  inner  surface 
can  react  with  the  outer  gas  layer,  so  that  CO  is  oxidized  to  C02 
and  H2  is  liberated.  Supposing  the  temperature  remains  constant 
or  decreases,  the  thermal  value  of  the  gas  remains  unchanged. 
If,  however,  the  average  temperature  of  the  gas  current  rises  - 
which  is  probable,  since  the  gas  comes  into  the  hotter  parts  of  the 
producer  —  this  reaction  decreases  and  the  actually  occurring 
improvement  in  the  quality  of  the  gas  cannot  be  explained  but 
by  oxidation  of  glowing  coal  by  means  of  the  C02  and  the  steam 
of  the  outer  layer  and  also  by  the  outward  diffusion  of  the  steam. 

If  we  work  according  to  the  " Parallelstrom  principle"  the  hot 
outer  layer  formed  in  the  start  will  react  vigorously  on  the  steam 
(on  account  of  the  higher  temperature  both  the  diffusion  and 
velocity  of  reaction  will  be  greater)  and  the  gas  without  practical 
change  in  thermal  value  will  get  richer  in  H2  and  poorer  in  CO. 
Hereby  the  quality  of  the  gas  is  improved,  just  the  same  as 
above,  by  the  reaction  of  the  outwardly  diffusing  steam  with  the 
glowing  coal.  On  the  other  hand,  the  gas  quality  is  deteriorated 
as  the  steam  gradually  comes  in  contact  with  cooler  coal,  whereby 
the  quantity  of  C02  is  increased. 

Undoubtedly  the  first  mentioned  way  of  gasifying  is  more 
advantageous,  the  more  so  as  in  this  case  the  gas  and  steam 
current  is  also  preheated  gradually. 

If  we  consider  the  average  composition  of  water  gas,  in  case 
the  state  of  equilibrium  is  not  reached,  we  always  find  this 
relation  between  C02,  CO,  and  H2,  that  the  volume  of  H2  is  equal 
to  the  sum  of  the  CO  volume  and  double  the  C02  volume.  Besides 
this  some  steam  is  also  present.  The  composition  of  the  wet 
water  gas  as  well  as  of  the  dry  gas  will,  therefore,  under  all  con- 
ditions correspond  to  one  equilibrium,  which,  however,  at  the 
same  steam  pressure  corresponds  to  another  (the  ideal)  gasify- 
ing temperature,  the  latter  being  lower  than  the  actual  gasifying 
temperature. 

Dr.  Hugo  Strache  and  R.  Jahoda  have  studied  the  influence 
of  height  of  fuel  and  air  and  steam  velocity  on  this  process,  both 
during  hot-blowing  and  gas  making,  and  have  found : 

In  the  beginning  of  the  hot-blowing  period  (when  the  tem- 
perature of  the  fuel  is  rather  low)  C02  is  formed  almost  exclusively 


284 


HEAT  ENERGY  A\D  FUELS 


without  any  CO,  while  with  increasing  temperature  the  forma- 
tion of  CO  increases.  We  have  here  again  the  equilibrium  which 
was  mentioned  before :  2  CO  +±  C02  -j-  C. 

As  less  C  is  absorbed  by  a  certain  volume  of  air  for  the  forma- 
tion of  C02  than  for  the  formation  of  CO,  the  fuel  consumption 
is  considerably  less  in  the  first  stages  of  hot-blowing  than  in  the 
later  stage,  while  the  quantity  of  heat  developed  per  minute  is 
very  much  greater  at  the  start  than  in  the  later  stages. 

The  loss  of  heat  by  the  hot  gas  leaving  the  producer  increases 
with  the  temperature.  The  heat  accumulated  in  the  producer 
is  evidently  equal  to  the  difference  of  generated  and  lost  heat. 
The  ratio  of  accumulated  heat  and  carbon  used  is  called  by 
Strache  "the  efficiency  in  hot-blowing."  This  ratio  is  high  in 
the  beginning  (at  low  temperature)  and  decreases  with  increas- 
ing temperature  and  fuel  consumption. 

Content  of  C02  and  efficiency  in  hot-blowing  are  as  follows  at 


Efficiency. 
Per  cent. 

C02. 
Per  cent. 

625°  C 

80 

18 

672°  C  .  .  . 

70 

16 

929°  C  
1300°  C  

40 
30 

7.6 
4  6 

The  total  efficiency  for  a  certain  blowing  period  decreases 
rapidly  between  650  and  900  degrees;  it  is  therefore  advan- 
tageous not  to  raise  the  temperature  of  the  producer  above 
900  degrees. 

The  losses  of  heat  during  the  hot-blowing  period  can  be 
utilized  to  a  large  extent  for  preheating  the  steam  (in  the  manu- 
facture of  pure  water  gas). 

The  losses  during  gas  making  depend  on  the  velocity  of  steam 
and  the  temperature  of  the  producer.  Too  low  velocity  yields 
a  rather  small  quantity  of  gas  and  causes  comparatively  great 
loss  of  heat  by  radiation;  too  great  velocity  is  disadvantageous 
on  account  of  the  steam  going  through  undecomposed ;  in  this 
case  large  quantities  of  heat  leave  the  producer  without  being 
utilized  on  account  of  the  high  specific  heat  of  steam. 


WATER  GAS 


285 


The  results  of  these  researches  are : 

1.  The  quantity  of  undecomposed  steam  and  the  C02  content 
of  the  gas  increase  at  constant  temperature  with  the  increasing 
velocity  of  the  steam  in  about  the  same  proportion. 

2.  The  content  of  steam  and  C02  of  the  crude  gas  at  constant 
velocity  of  steam  decreases  with  increasing  temperature. 

3.  Even  at  low  temperature  the  content  of  C02  and  steam 
can  be  reduced  to  a  minimum  by  decreasing  the  velocity  of  steam. 


700    800    900    1000   1100   1200   1300   1400   1500   1600   1703 

FIG.  93.  —  Efficiency  of  Water  Gas  Making  Referred  to  Velocity  of  Steam. 

The  efficiency  in  gas  making  is  calculated  from  the  carbon 
consumption  during  gas  making,  loss  of  heat  in  the  producer, 
and  the  thermal  value  of  the  water  gas  produced.  The  total  heat 
loss  is  made  up  of  the  heat  of  formation,  heat  of  the  gas  pro- 
duced and  of  the  undecomposed  steam,  and  the  radiation  of  heat 
from  the  producer.  For  every  temperature  there  is  a  certain 
velocity  of  steam,  with  which  a  maximum  efficiency  is  reached 
(87  to  93  per  cent). 


286  HEAT  ENERGY  AND  FUELS 

The  total  efficiency  for  any  given  velocity  of  steam  can  be 
calculated  from  the  carbon  consumption  during  blowing  and 
gas  making  and  from  the  loss  of  heat  during  blowing  and  gas 
making. 

Fig.  93  shows  a  diagram  of  these  conditions. 

The  total  efficiencies  also  show  a  maximum  at  a  certain  velocity 
of  steam. 

At  780°  C 72.5  per  cent, 

At  860aC 77     per  cent. 

SUGGESTIONS  FOR  LESSONS. 

Experiments  analogous  to  those  under  generator  (air)  gas  can 
be  made. 


CHAPTER  XXII. 

DOWSON  GAS,  BLAST-FURNACE  GAS,  AND  REGENERATED 
COMBUSTION  GASES. 

THE  production  of  pure  water  gas  has  the  advantage  of  fur- 
nishing a  gas  of  high  absolute  and  pyro metric  efficiency,  which 
is  of  importance  for  certain  purposes. 

Besides  the  fact  that  this  gas  cannot  be  generated  except  by 
employing  external  energy  (for  decomposing  steam)  and  by 
using  an  expensive  boiler  plant,  the  producer  gas  which  is  herein 
obtained  as  by-product  with  a  high  percentage  of  carbon  dioxide 
can  be  used  mostly  for  auxiliary  purposes  only.  Furthermore 
this  process  has  two  disadvantages : 

1.  It  is  an  intermittent  process  (two  stage),  comparatively 
difficult,  complicated,  and  expensive. 

2.  It  requires  a  plant  of  double  the  size  of  that  of  a  continuous 
process. 

The  idea  presented  itself  of  having  the  two  processes  of  hot- 
blowing  and  gas  making  take  place  in  parallel  and  simultaneously 
in  one  producer,  whereby  Dowson  gas  or  semi-water  gas  (some- 
times also  called  producer  gas)  is  obtained. 

The  purpose  of  this  process  being  the  generation  of  gas  of  the 
highest  possible  heating  value,  the  amount  of  carbon  dioxide 
has  to  be  kept  as  low  as  possible.  Since  with  decreasing  carbon 
dioxide  the  nitrogen  content  considerably  increases,  the  thermal 
value  of  the  gas  decreasing  at  the  same  time,  this  point  deserves 
serious  consideration. 

We  will  now  consider  the  ideal  conditions.  The  reaction 
C  +  H20  =  CO  +  H2  takes  place  with  the  consumption  of 
42,900  cal.  for  every  12  g.  of  carbon  gasified,  while  in  the  reaction 
C  +  i  (Oa)  =  CO  21,100  cal.  are  liberated  for  every  12  g.  of 
carbon. 

Therefore  in  order  to  keep  the  temperature  of  the  producer 
constant,  we  have  to  get  as  much  heat  from  the  second  process 
as  is  consumed  by  the  first  process  (not  considering  the  losses  of 

287 


288  HEAT  ENERGY  AND  FUELS 

heat).  We  therefore  have  to  gasify  two  atoms  of  carbon  with 
air  for  every  atom  of  carbon  gasified  with  steam.  The  ideal 
equation  for  this  process  is 

3  C  +  H20  +  02  +  4  N2  =  3  CO  +  H2  +  4  N2> 

which  is  equivalent  to  a  Dowson  gas  of  the  following  composition : 

CO 37.5 

H2 12.5 

N..  .  50.0 


100.00 
In  the  reaction 

C  +  2  H20  =  C02  +  2  H2, 

on  the  other  hand,  for  every  12  g.  of  carbon  40,400  cal.  have  to 
be  furnished  by  gasifying  with  air.  This  is  also  one  atom  of 
carbon  gasified  with  steam  to  two  atoms  of  carbon  gasified  with 
air.  The  ideal  equation  is 

3  C  +  2  H20  +  02  +  4  N2  =-C02  +  2  H2  +  4  N2  +  2  CO, 

the  analysis  of  the  gas : 

C02 11.1 

CO 22.2 

H2 22.2 

N2 45.5 

101.0 

In  working  with  coal  instead  of  with  carbon,  volatile  matters 
enter  this  reaction,  whereby  the  nitrogen  content  is  further 
decreased. 

In  practice  —  on  account  of  unavoidable  losses  —  more  than 
two  atoms  of  carbon  have  to  be  gasified  with  air  for  every  atom 
gasified  with  steam. 

The  equilibrium 

CO  +  H20  <=»  C02  +  H2 

causes  the  formation  of  steam,  which  can  considerably  deteriorate 
the  quality  of  the  gas. 
The  principle  of  this  process  is  the  oxidation  of  carbon  partly 


GASES  289 

by  oxygen  of  the  air  and  partly  by  oxygen  of  an  oxide  (water). 
A  similar  reaction  takes  place  in  the  blast  furnace,  where,  besides 
the  oxygen  of  the  air,  the  oxygen  of  the  iron  oxide  is  used  for 
oxidizing  the  carbon  mainly  according  to 

3  C  +  Fe203  =  2  Fe  +  3  CO, 

and  to  a  small  extent  according  to 

3  C  +  Fe203  =  4  Fe  +  3  C02. 

The  ordinary  composition  of  blast-furnace  gas  is 

Average 

C02 5-16  12 

CO 20-32  24 

H 0.1-4.5  2 

CH4 0.2-2.5  2 

N2 56-63  60 

Blast-furnace  gas  has  a  fairly  high  thermal  value.  The  source 
of  the  hydrogen  in  this  gas  is  the  air  moisture,  which  acts  on  the 
carbon;  the  methane  content  is  very  probably  caused  by  direct 
synthesis.  Since  a  considerable  part  of  the  oxygen  of  the  blast- 
furnace gas  is  derived  from  the  ore  instead  of  the  atmosphere, 
the  quantity  of  nitrogen  in  furnace  gas  is  lower  than  in  producer 
gas  generated  by  an  exclusive  oxidation  by  means  of  air.  The 
content  of  carbon  dioxide  is  partly  explained  by  conditions  of 
equilibrium  (in  the  cooler  part  of  the  furnace  some  of  the  carbon 
monoxide  is  decomposed  according  to  2  CO  =  C02  +  C)  and 
partly  by  the  reduction  process  (3  CO  +  Fe203  =  3  C03  +  2  Fe). 

Instead  of  using  the  oxygen  of  water  or  oxides  of  metals  for 
partly  oxidizing  carbon,  the  oxygen  of  carbon  dioxide  can  be 
used:  C  +  C02  =  2  CO. 

This  can  be  done  by  passing  gases  rich  in  carbon  dioxide 
through  a  glowing  layer  of  coal,  which  process  is  called  regenera- 
tion. Such  "  regenerable "  gases  are  for  instance  combustion 
gases  and  gases  from  lime  kilns  or  blast  furnaces.  The  last 
named  gas  seems  to  be  especially  adapted  on  account  of  the  small 
amount  of  nitrogen  present. 

If  we  should  succeed  in  converting  by  this  process  the  total 
carbon  dioxide  of  a  blast-furnace  gas  of  the  above  average 


290  HEAT  EX  ERG  Y  AND  FUELS 

analysis  into  carbon  monoxide,  a  gas  of  the  following  composition 
would  be  obtained: 

60 

N  =    — —  =  53 . 58  per  cent, 

CO  =  24  *2  *  12  =  42.86  per  cent, 

_L  .  \.2i 

CH4=  ——  =     1 . 78  per  cent, 

2 

H  =  — -  =    1 . 78  per  cent, 

the  thermal  value  of  which  would  be  considerably  higher  than 

that  of  the  original  gas. 

The  heat  consumption  for  this  process  is  as  follows : 
The    reaction    C02  +  C  =  2  CO  absorbs  97,600-2  X  26,100 
-  45,400  cal.     If  we  want  to  reclaim  this  amount  of  heat  (as 

with  Dowson  gas)  by  the  reaction  C  +  0  =  CO  +  21,100  cal., 

we  have  to  transform  for  every  mol  of  carbon  dioxide  contained 

45  4 
in  the  gas  — '--  or  about  2  atoms  of  carbon  into  air-producer  gas. 

We  get  about  the  same  conditions  as  with  water  gas,  and  in  prac- 
tice we  will  have  to  burn,  instead  of  2  mols  carbon,  from  3  to  5 
mols  to  carbon  monoxide.  Supposing  we  should  get  2  mols  of 
carbon  monoxide  by  direct  combustion,  for  every  mol  of  carbon 
dioxide,  we  would  have  the  following  theoretical  composition  for 
the  regenerated  blast-furnace  gas: 


1  .81 


_  58.06  per  cent, 


94.  4-  4  V  1  9 

CO  =       \     *       =  39  .  74  per  cent, 
1  .81 

CH4  =  —  —  =  1  .  10  per  cent, 

1  .81 

2 

H2=  —  —  =  1.10  per  cent. 
1  .  81 

As  above  stated  a  larger  part  of  the  carbon  will  have  to  be 
burned  in  practice  on  account  of  unavoidable  losses  in  heat. 


GASES  291 

Supposing  we  take  3  gram-atoms  of  carbon  for  every  mol  of 
dioxide  to  be  reduced,  we  get  a  gas  of  the  following  theoretical 
composition  : 

N^6°t!!-71  -59.21  per  cent, 
2.1o 

CO  =  ^  +3+  ^  =  38'93 


CH4=  ~=   0.93  per  cent, 

Zi  .  It) 

H2=  -2—  =    0.93  per  cent. 

—  .  J.O 

In  practice  this  result  could  be  obtained  only  by  applying  a 
sufficiently  high  gasifying  temperature,  as  otherwise  the  reaction 
would  be  incomplete.  So  far  this  method  is  not  in  practical  use. 


SUGGESTIONS  FOR  LESSONS. 

Production  of  Dowson  gas,  same  as  in  the  two  former  lessons. 
Effect  of  air  and  carbon  dioxide  upon  a  layer  of  glowing  coal. 


CHAPTER  XXIII. 
APPARATUS    FOR   THE    PRODUCTION    OF   FUEL   GASES. 

(GENERATOR  OR  PRODUCER  GAS  PLANTS.) 

THE  apparatus  which  are  used  in  practice  for  manufacturing 
fuel  gases  are  called  gas-generators  or  gas-producers.  These 
are,  generally  speaking,  chambers  lined  with  firebrick.  These 
chambers  are  charged  with  coal,  wood  or  peat  respectively,  and 
the  air  of  combustion  or  steam  or  a  mixture  of  steam  and  air  is 
passed  through,  generally  upward. 

If  air  (generator)  gas  is  produced  the  gas  in  the  producer  is 
moved  either  by  draft  (chimney)  alone  or  by  pressure  (blower). 
Accordingly  we  have  a  classification  in  draft  and  pressure- 
producers.  The  latter  have  to  be  closed  tight  at  the  bottom. 


FIG.  94.  —  Boetius  Gas  Generator. 


We  shall  consider  first  the  air-gas  generators,  which  were  built 
originally  right  near  the  furnace,  which  was  to  be  heated 
(Siemens  gas  or  half-gas).  Their  development  is  shown  by  the 
following  types : 


FUEL  GASES 


293 


Fig.  94.  Boetius  producer.  The  producer  compartment,  G, 
is  separated  from  the  combustion  chamber  of  the  furnace  by  a 
vertical  wall  and  from  the  outside  atmosphere  by  an  inclined 
wall  upon  which  the  charged  coal  slides  down.  The  opening,  a, 
for  the  charge  can  be  closed  by  means  of  the  slide,  ss.  The 
inclined  wall  is  supported  by  the  iron  bar,  6,  which  contains  an 


FIGS.  95  and  96.  —  Boetius  Double  Generator. 

opening  for  poking  and  air-admission.  At  the  bottom  the 
producer  compartment,  G,  is  separated  from  the  ashpit,  A,  by 
the  inclined  grate,  r.  The  channels,  c,  in  the  back  wall  allow  a 
preheating  of  the  air  of  combustion. 

Figs.  95  and  96.     Boetius  double  producer,  developed  from 
the  former  type  by  combining  two  producers  (right  and  left) 


FIGS.  97  and  98.  —  Bicheroux  Generators. 

and  leaving  out  the  back  walls.  Thereby  less  brickwork  is 
required  and  loss  by  radiation  from  the  back  wall  avoided  (at 
the  same  time  doing  away  with  the  preheating  of  air).  We  find 
here  the  air-channels  in  the  side  walls.  The  inclined  grate  is 
supplanted  by  a  plane-grate.  R  is  the  grate,  c  the  air-channels. 
Larger  than  these  are  the  Bicheroux  producers  (Figs.  97  and 
98)  which  are  provided  either  with  step-grate,  T,  and  inclined 


294 


HEAT  ENERGY  AXD  FUELS 


grate,  R,  or  with  a  plane-grate,  r.    f  is  the  charging  opening. 
These  producers  are  also  built  right  near  the  fireplace. 

Largely  used  are  the  shaft  producers  of  William  and  Friedrich 
Siemens.     They  are  built  independent  of  the  furnace  to   be 


IV 


III 


FIGS.  99  and  100.  —  Siemens  Generator. 

heated.  In  order  to  avoid  as  far  as  possible  losses  of  heat  and 
to  save  brickwork  they  are  frequently  built  below  the  floor  level 
in  rows  or  in  squares.  Figs.  99  and  100  show  a  plant  of  the  latter 
kind  in  elevation  and  ground  plan.  Fig.  99  shows  two  producers 
with  one  common  wall.  These  producers  are  provided  with 
step-grates,  T,  and  inclined  grate,  R.  The  ground  plan  shows 
four  producers  I,  II,  III  and  IV,  arranged  in  the  form  of  a  square. 


FUEL  GASES 


295 


There  are  two  charging  chutes  for  each  producer;  the  holes,  s, 
are  for  poking  the  fire.  The  gas  leaves  all  four  producers  through 
one  gas  main.  The  back  wall  of  these  producers  is  inclined,  for 
preventing  the  air  from  passing  along  the  vertical  wall  (least 
resistance). 

A  charging  hopper  is  shown  in  Fig.  101.     Same  is  provided 
with  a  valve  operated  by  a  counterweight  and  a  cover  which 

Cover 


FIG.  101.  —  Charging  Hopper. 

closes  gas-tight  by  means  of  a  sand  or  tar  seal.  For  charging 
coal  the  cover  is  removed,  coal  filled  in,  the  cover  put  on  and 
then  the  valve  opened.  Thereby  losses  of  gas  are  prevented. 

In  order  to  increase  the  fuel  height,  (7,  which  is  to  be  measured 
in  the  direction  of  the  arrows,  in  some  cases  the  charging  hopper 


FIG.  102.  —  Siemens  Generator  of  Neuberg. 

has  been  moved  more  toward  the  center  (Fig.  102).  For  dis- 
connecting one  producer  of  a  producer  system,  valves,  V,  are 
provided.  Below  the  ash-pit  there  is  an  excavation  filled  with 
water,  the  latter  being  evaporated  by  the  ash  and  fuel  falling 
through  the  grate,  whereby  the  quality  of  the  gas  is  improved 
(Dowson  gas). 
If  we  omit  one  of  the  two  separating  walls  in  a  square  of 


206 


HEAT  ENERGY  AXD  FUELS 


FIG.  103.  —  Siemens  Double  Generator. 


FIGS.  104  and  105.  —  Old  Shaft  Generator  of  Donawitz. 


FIG.  106.  —  Generator  of       FIG.  107.  —  Bituminous  Coal  Generator 
Kolsva.  of  Odelstjerna. 


FUEL  GASES 


297 


four  Siemens  producers,  we  arrive  at  double  producers  (Fig. 
103)  which  can  be  built  singly  or  in  rows. 

Shaft  producers  (old  Donawitz  type)  for  lignite  and  brown 
coal  are  shown  in  Figs.  104  and  105.  The  inclined  step,  a,  in  the 
brick  lining  is  necessary  for  preventing  the  rising  of  the  air 
alongside  the  walls.  Other  types  of  shaft  producers  are : 

The  producer  of  Kolsva  in  Sweden  (Fig.  106)  in  which  Parry's 
hopper,  p,  is  used  for  charging. 

The  different  types  of  producers  of  Odelstjerna  are : 

(a)  For  bituminous  coal  (Fig.  107).     This  producer  is  wider 
at  the  bottom  to  facilitate  the  downward  movement  of  the  coal. 
For  preventing  the  rising  of  the  air  alongside  the  wall  an  offset 
is  arranged  at  the  bottom  of  the  shaft. 

(b)  For  peat,  wood  and  shavings  (Fig.  108).     For  these  fuels 
the  shaft  has   to  be   considerably  wider  and  the   fuel-height 


FIG.  108.  —  Odelstjerna 's  Generator 
for  Peat,  Wood  and  Shavings. 


FIG.  109.  —  Generator  of  Tholander. 


greater  than  for  coal.  A  plane  or  step-grate  is  used  in  these  pro- 
ducers, which  are  generally  arranged  for  blast  and  provided  with 
air-tight  doors,  T.  The  soft  coal  producer  of  Tholander  (Fig. 
109),  which  is  of  peculiar  shape,  is  arranged  for  air  blast  at  the 
bottom.  In  this  construction  the  active  height  of  fuel  (i.e.  the 
way  along  which  the  primary  air  comes  in  contact  with  glowing 
coal,  ab)  is  kept  constant  at  all  periods.  The  fuel  rests  on  a  solid 
base,  cd.  F  is  the  charging  hopper,  ww  is  the  blast-channel,  G  the 


298 


HEAT  ENERGY  AND  FUELS 


producer-shaft,  ss  are  the  poke-holes  and  TT  the  ash-cloors.  As 
seen  from  the  above  descriptions  the  cross-sections  of  producers 
are  made  both  square  and  circular.  In  single  (isolated)  pro- 


Li  11     I 


FIG.  110.  —  Funnel-Shaped  Grate. 


FIG.  111.  —  Conical  Grate. 


ducers  the  circular  cross-section  is  of  advantage  on  account  of 
more  uniform  operation  and  smaller  loss  of  heat  by  radiation. 
They  are  provided  either  with  a  plane-grate  (as  in  the  Odelstjerna 


FIG.  112.  —  Conical  Grate. 


FIG.  113.  —  Bottom  of  Generator 
with  Step  and  Plane  Grate. 


type  for  peat,  wood,  etc.),  or  with  a  funnel-shaped  or  conical 
grate  (Figs.  110,  111  and  112). 

Less  advantageous  is  the  combined  use  of  two  step-grates  and 
one  plane-grate  (Fig.  113). 


FUEL  GASES 


299 


Plane-grates  can  be  used  only  for  large-size  fuels  as  fuel  of 
small  grain  would  fall  through  the  grate-bars.  Step-grates  have 
to  be  used  for  the  latter  fuel.  In  many  cases  the  Lichtenfel's 
construction  of  plane  and  step-grates  is  convenient,  which  com- 
bines the  good  points  of  plane  and  step-grates  (Fig.  114).  The 


FIG.  114.  —  Lichtenfel's  Plane  Step  Grate. 

trouble  of  cleaning  the  grate  is  reduced  to  a  minimum  if  the  grate- 
bars  1,  3  and  5  are  arranged  unmovable  while  2  and  4  are  kept  in 
motion  at  a  right  angle  to  the  elevation  of  the  producer,  as 
thereby  most  of  the  ash  falls  through  automatically. 


FIGS.  115  and  116.  —  Turnable  Eccen- 
tric Cone-Grate. 


FIG.  117.  —  A.  Sailler's  Pressure  Pro- 
ducer with  Slag  Openings. 


The  same  effect  is  reached  by  revolving  conical-grates,  espe- 
cially if  the  axis  of  rotation  and  axis  of  the  cone  are  not  the 
same  (Figs.  115,  116).  Such  an  eccentric  cone-grate  can  be 
mounted  upon  a  circular  base-plate,  which  moves  in  a  channel. 


300 


HEAT  ENERGY  AND  FUELS 


If  the  plate  is  provided  with  teeth  around  the  edge  it  can  be 
driven  by  a  simple  worm  gear. 

On  the  other  hand  some  rather  complicated  stirring-arrange- 
ments have  been  put  on  circular  producers. 

In  pressure  producers  a  grate  is  not  an  absolute  necessity,  as 
we  have  seen  on  Tholander's  producer.  It  is  of  advantage  to 
work  without  grate,  if  badly  clinking  and  coking  fuel  is  used,  in 
which  case  it  is  frequently  advantageous  to  add  a  flux  to  the  fuel 
for  forming  an  easily  fusible  slag,  which  is  let  off  from  time  to 
time.  Saillers'  producer  (Fig.  117)  shows  such  a  construction. 


FIG.  118.  —  Steam  Jet-Blower  for  Dowson  Gas  Generator 


/is  the  charging  arrangement,  ss  are  the  poke-holes,  WW  the 
blast  channel,  aa  slag  openings. 

A  convenient  device  for  preventing  the  escape  of  gas  during 
poking  was  designed  by  Hofmann  and  Stache.  A  steam  coil 
of  pipe  perforated  on  the  side  toward  the  center  of  the  coil  is 
arranged  around  the  poke-hole.  If  one  of  the  holes  is  opened  a 
steam  valve  is  opened  automatically  and  steam  blown  through 
the  perforations,  which  prevents  the  escape  of  gas. 

The  disadvantages  caused  by  putting  green  fuel  into  the  pro- 
ducer from  time  to  time,  namely  non-uniform  temperature  of 
the  producer  and  uniform  composition  of  the  gas,  was  the  rea- 
son for  experiments  to  separate  the  process  of  distillation  from 
the  process  of  gasification.  Such  suggestions  were  made  by 
Minary,  Brook  and  Wilson,  Kleeman,  C.  Neese,  Groebe-Luhr- 
mann,  Wilhelm  Schmidhammer,  Fr.  Toldt,  etc.  All  these  pro- 
ducers are  rather  complicated  and  better  result  can  be  obtained 
more  conveniently  by  combining  a  number  of  producers. 

The  manufacture  of  Dowson  gas  in  draft-producers  is  effected 


FUEL  GASES  301 

by  arranging  a  water-basin  below  the  grate.  By  the  radiating 
heat  of  the  grate-bars  and  the  hot  ash  falling  through,  water  is 
evaporated  and  with  the  air  carried  through  the  producer. 

In  pressure  producers  air  and  steam  are  either  led  under  the 
grate  separately  (which  allows  independent  regulation  of  air 
and  gas)  or  a  steam  jet-blower  is  used,  which  draws  in  the  air 
(Fig.  118). 

The  condensation  of  the  products  of  distillation  in  the  producer 
gas  by  cooling  and  washing  is,  under  ordinary  conditions,  unec- 
onomical, as  both  by  cooling  and  condensation  considerable 
quantities  of  heat  are  lost. 

The  apparatus  for  producing  pure  water-gas  will  be  considered 
later. 

SUGGESTIONS  FOR  LESSONS. 

A  producer  gas  plant  is  to  be  designed  for  a  certain  amount  of 
heat  required  per  hour  and  a  fuel  of  known  composition  and  gas- 
yield.  Herein  secondary  circumstances  can  also  be  considered 
(plan  of  the  floor  space  at  disposal,  convenient  transportation  of 
coal  to  the  producers,  reserve-producers,  coal  storage,  etc.). 

An  existing  draft-producer  plant  is  to  be  changed  into  pressure- 
producers  or  into  a  Dowson-gas  plant. 

An  existing  producer  plant  is  to  be  enlarged,  so  as  to  yield 
double  the  amount  of  gas. 


INDEX 


Absorbing  capacity  of  coals,  199. 
Air,  surplus,  for  combustion,  258. 
Alloys  — 

melting  points  of,  54. 

Princep's,  53. 

Ammonia  available  in  coals,  222. 
Analysis  of  — 

anthracites,  186. 

ash,  151. 

bituminous  coal,  184,  185. 

brown  coal,  173. 

brown  coal- ash,  177. 

peat,  168,  171. 

producer  gas,  256. 

products    of    destructive    distilla- 
tion, 216,  217. 

Anthracites,  analysis  of,  186. 
Arth's  formula,  115. 
Artificial  fuels  — 

gaseous,  243. 

solid,  143,  188. 
Ash- 

analyses,  151. 

content  of  peat,  169. 
of  wood,  149,  150. 

Berthier's  method,  111. 

Bessemer  converter,  temperature  in, 

72. 
Bituminous  coal  — 

analysis,  184,  185. 

classification,  178. 

destructive  distillation,  215. 

generating  gas  from,  265. 
Blast  furnace  — 

gas,  287. 

temperature  in,  72. 
Boiling  and  melting  points,  51. 
Briquettes,  228. 

composition  of  lignite,  229. 


Brown  coal  — 
analysis,  173. 
ash,  177. 
classification,  174. 

Calculation  of  thermal  values,  110. 
Calibrating  pyrometers,  83. 
Calorimeter  — 

Fischer,  64,  93. 

Mahler,  94. 

Parr,  100,  104. 

Weinhold,  61. 

Carbon  dioxide,  dissociation  of,  120. 
Carbonaceous  decomposition,  156. 
Charcoal,  191. 

absorbing  capacity,  199. 

classification,  199. 

composition,  192. 

temperature  of  ignition,  199. 

weight,  198. 
Charring,  193. 

with  steam,  208. 

yield  of,  194-196. 
Classification  — 

charcoal,  199. 

coal,  174,  178,  180. 

fuel,  141. 

peat,  166. 

wood,  145. 
Coal- 

ammonia  available,  222. 

yield  from  destructive  distillation 

of,  221. 
Coke  oven  — 

Coppee,  235. 

Francois,  235. 

Frangois-Rexroth,  233. 

Dr.  Otto,  235. 

gas,  223. 

Smet,  233. 

tar,  222. 


303 


304 


INDEX 


Coking  apparatus,  231. 
Combustion  — 

data,  130. 

gases,  regenerated,  287. 

heat,  91,  105,  108. 

incomplete,  117. 

of  producer  gas,  139. 

products  of,  262. 

surplus  air  for,  258. 

temperature  of  coal,  136. 

of  producer  gas,  138. 
Composition  — 

of  coals,  221. 

of  fuels,  142,  157,  160.' 

of  Kiln  gases,  204. 

of  peat,  169. 

of  products  of  destructive  distilla- 
tion, 190. 

of  wood,  148. 
Cones  — 

composition  of,  57,  58. 

melting  points  of,  56. 

Seger,  55. 

Content  of  wood,  actual,  147. 
Coppee  oven,  235. 
Crony  oven,  237. 

Data  on  charring,  193. 
Decomposition,  carbonaceous,  156. 
Depression  of  glass,  38. 
Destructive  distillation  — 

analysis,  216,  217. 

effect  of  admixtures,  220. 

of  coal,  composition  of  products  of, 
190. 

of  coal,  yield  from,  221. 

of  bituminous  coal,  215. 

of  peat,  214,  224,  225,  226. 
Determination  of  thermal  value,  92. 
Dissociation  of  carbon  dioxide,  120. 
Distillation,  products  of,  262. 
Distribution  of  heat,  263. 
Dowson  gas,  287. 

Economy  of  operation,  8. 
Elementary  composition  of  coal  and 

products  of  combustion,  262. 
distillation,  262. 


Elementary  composition  of  producer 

gas,  257. 

Emissive  power  of  substances,  73. 
Energy  — 

changes  of,  12. 

chemical,  change  of,  26. 

distance,  14. 

electric,  27. 

forms  of,  13. 

of  reaction,  24. 

radiant,  30. 

radiation  of,  78. 

surface,  16. 

volume,  25. 

Errors  in  the  measurement  of  temper- 
atures, 38. 

Evaporating  power  of  wood,  153. 
Explosives,  124. 
External  work,  132. 

Fery's  thermoelectric  telescope,  79. 
Fischer  calorimeter,  64,  93. 
Formula  — 

Arth,  115. 

Gmelin,  112. 

Goutal,  116. 
Frangois  oven,  235. 
Frangois-Rexorth  oven,  233. 
Fuels  — 

artificial  solid,  143. 

classification  of,  141. 

composition  of,  142,  157,  160.       . 

formation  heat  of,  161. 

liquid,  241. 

composition  of,  241,  242. 

natural  solid,  142. 

thermal  efficiency  of,  242. 
Fuel  gases  — 

production  of,  244. 

value  of  wood,  153. 
Furnace,  ideal,  128. 

Gas,  producer,  246. 
analysis,  256. 

elementary  components,  257. 
influence    of    temperature    in    the 

manufacture  of,  247. 
ideal  composition  of,  249,  250,  251. 


INDEX 


305 


Gases  — 

combustion  temperature,  135. 
mixed  distillation  and  combustion, 

261. 

specific  heat,  129. 
Gasifying  temperature,  259. 
Generator  — 

gas  from  bituminous  coal,  265. 
lignite,  266. 
peat,  265. 
wood,  264. 
gas  plants,  292. 
heat  distribution  in,  263. 
Glass,  standard  thermometer,  39. 
Glow  colors  — 

temperatures  corresponding  to,  69. 

of  silver,  71. 
Gmelin's  method,  112. 
GoutaPs  formula,  116. 
Grates  — 

for  producers,  297,  298. 
Lichtenfels',  298. 

Hartmann  and  Braun's  pyrometer,  81. 
Heat  — 

capacities,  66. 

combustion,  91. 

distribution,  263. 

of  combustion  products,  138. 

Ideal  furnace,  128. 
Illuminating  flames,  123. 
Illuminating  gas,  223. 
Incomplete  combustion,  117. 
Increase  of  value  of  a  substance,  7. 

Kiln  gases,  composition  of,  204. 
Klinghammer's  thalpotasimeter,  52. 

Law  — 

Joule's,  30. 

Ohm's,  29. 

Lichtenfels'  grate,  298. 
Light,  intensities  of,  74. 
Lignite    briquettes,    composition    of, 

229. 
Liquid  fuels,  241. 

composition  of,  241,  242. 
Lottmann  oven,  237. 


Mahler's  calorimeter,  94. 
Measurements  — 

pyrometrical,  80,  81. 

with  thermoelements,  82. 
Melting  point  — 

of  alloys,  54. 

of  metals,  60. 
Mixed    distillation    and    combustion 

gases,  261. 
Moisture  in  wood,  150,  151. 

Natural  gas,  composition,  243. 
Natural  solid  fuels,  142. 

Odelstjerna  producer,  297. 
Optical  methods  of  measuring  tem- 
peratures, 68. 
Otto  oven,  235. 
Oven,  pile  retort,  212. 

Parr,  calorimeter,  100,  104. 
Peat  — 

analysis,  168,  171. 

ash  content,  169. 

classification,  166. 

coke  ovens,  237. 

composition,  169. 

destructive   distillation,    214,    224, 
225,  226. 

generator  gas,  265. 

thermal  value,  170. 
Pile  oven,  206. 
Piles,  202. 

Poking  producers,  300. 
Potential,  chemical,  22. 
Princep's  alloys,  53. 
Producers  — 

grates,  297,  298. 

Odelstjerna,  297. 

poking,  300. 

Siemens,  294. 

Tholander,  297. 
Producer  gas,  246. 

analysis,  256,  269. 

elementary  components,  257. 

ideal  composition  of,  249,  250,  251. 

influence    of    temperature    in    the 
manufacture  of,  247. 

plants,  292. 


306 


INDEX 


Production  of  fuel  gases,  244. 
Pyrometer  — 

calibrating,  83. 

of  Cornu  Le  Chatelier,  73. 

of  Hartmann  and  Braun,  81. 

of  Mesure  and  Nouel.  68. 

of  Wanner,  75. 

of  Weinhold,  61. 

polariscopic,  71. 

water  (Siemens),  67. 
Pyrometrical  measurements,  80,  81. 
Pyroscopes,  composition,  57,  58. 

Resin  content  of  wood,  149. 

Seasoning  of  wood,  152. 
Seger  cones,  55. 

composition  of,  57,  58. 

melting  points  of,  56. 
Siemens'  producer,  294. 

water  pyrometer,  67. 
Smelting  furnace,  123. 
Smet  oven,  233. 

Solid    substances,    combustion    tem- 
perature of,  135. 

Specific  gravity  of  woods,  145,  146. 
Specific  neat  of  gases,  129. 
Superheated  steam  for  charring,  208. 

Tar  from  coke  ovens,  222. 
Temperatures  — 

corresponding  to  glow  colors,  69. 

determination,  75,  77,  86. 

gasifying,  259. 

measurement  of  high,  37. 

of  ignition  of  charcoal,  199. 

optical  methods  of  measuring,  68. 
Thalpotasimeter,  52. 
Thermal  value  — 

Berthier's  method  for  determining, 
111. 

calculation,  110. 

direct  determination,  92. 

Gmelin's  method,  112. 

of  peat,  170. 

of  wood,  152. 


Thermodynamic  laws,  19. 
Thermoelectric  telescope,  7:). 
Thermoelements,  85. 

measurements  with,  82. 
Thermometers,  37. 

correction  factors,  40. 

gas  or  air,  43. 

reading  of,  39. 
Thermophone,  87. 
Tholander's  producer,  297. 

Vignoles'  oven,  237. 

Wanner  pyrometer,  75. 
Water  gas,  268. 

carbon  content,  279. 

combustible  gases  in,  275. 

composition  of,  269. 

effect  of  steam  pressure  and  tem- 
perature, 272,  282. 

equilibrium,  271. 

quantity    of    steam    required    for 
formation  of,  278,  281. 

theory  of,  283. 

thermal  value  of,  275. 
Weight  of  wood,  148. 
Weinhold ;s  pyrometer,  61. 
Wiborgh's  thermophone,  87. 
Wood,  145. 

actual  content  of,  147. 

ash  content  of,  149,  150. 

classification  of,  145. 

composition  of,  148. 

distillation  of,  191. 

evaporating  power  of,  153. 

generator  gas  from,  264. 

moisture  in,  150,  151. 

resin  content  of,  149. 

seasoning,  152. 

specific  gravity  of,  145,  146. 

thermal  value,  152,  153. 

weight  of,  148. 
Work,  external,  132. 

Yield  from  destructive  distillation  of 
coals,  221. 


OF  THE 

(    UNIVERSITY   | 


The   Mechan ical   Appl iances 


OF  THE 


Chemical   and  Metallurgical 
Industries 

BY  OSKAR  NAGEL,  PH.D. 

A  Detailed  Description  of  all  Machines,  Appli- 
ances and  Apparatus  Used  in  the  Chemical 
and  Metallurgical  Industries. 

THE   ONLY  AMERICAN    BOOK   ON  THIS   SUBJECT 


CONTENTS 

I.  General.  II.  Steam  and  Water  Power.  III.  Gas 
Power.  IV.  Electric  Power.  V.  Transportation  of 
Solids.  VI.  Transportation  of  Liquids.  VII.  Trans- 
portation of  Gases.  VIII.  Grinding  Machinery. 
IX.  Mixing  Machines.  X.  Firing  and  Furnaces. 
XI.  Separating  Machines.  XII.  Purification  of 

Gases.     XIII.  Evaporating,  Distilling  and  Condens- 
ing.     XIV.  Drying. 


300  Pages         8vo.        292  Illustrations 

Price,  $2.00 
Sent  Anywhere  on  Receipt  of  Price 

OSKAR  NAGEL 

P.  O.  Box  385  NEW  YORK 


